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Caps, covers and clips

Lost a cap nobody sells?

One rider bought a whole new Sigma STS sensor because the battery cap isn't sold alone; Sigma lists the sensor at €29.95. We draw the missing part from a photo and print it. Same with Urban Arrow's rain cover: we found no separate clips in its catalogue (checked October 2026), only the €379 cover. If the twin is still on the bike, two photos of it in place with a ruler are enough to start.

Section drawing of a Sigma STS sensor on a frame tube: on the left the battery well with the cell and no cap, a red dimension across the whole sensor; on the right the sensor dashed and only our cap with its O-ring, an orange dimension across the cap.
Off the shelf: the whole STS sensor, €29.95, when only the cap is gone.Ours: the cap alone, with its O-ring, two in a pack for €19.

Drawing. Sensor and cap shapes approximate.

From €19

Tell us your bike →See the designs ↓

Pay after you approve the drawing · Doesn't fit? Refund or a better part · STEP file included · Datar P.S.A., Warsaw

The first ten bike orders ship free within the EU, and their photos go on this page if you agree.

Why it fails

Why nobody sells the cap alone

Small plastic parts are cheap to make and expensive to stock, so makers sell the whole assembly or nothing. Folding and cargo bikes carry the most of them. With one surviving twin, or a careful photo, we can draw the part and keep the file for the next one.

Designs

What we'd draw for your bike

Battery cap for a Sigma STS sensor, two in a pack

A coin-slot cap with a bayonet and an O-ring, two in the pack, because the next one falls off too.

Render from the front: a clay-grey Sigma STS-style sensor zip-tied to a tube, our black cap in its battery well with a fluted rim, CR2032 above a horizontal coin slot and a tick lined up with a dot on the sensor.
Example design · render
Fits
Sigma STS sensors with a CR2032 under a coin-slot cap: BC 14.16 STS, BC 12.12 STS, STS Speed Transmitter 00541. Other CR2032 sensors from a photo of the open well
Bolts to
A three-lug bayonet in the sensor's own battery well, turned 60° with a 10-cent coin like the original
Mass
2.7 g each, CAD estimate
Material
ASA, NBR O-ring
Hardware
None. A bought NBR O-ring sits in a groove, sized to your well
Torque
None: hand tight with a coin, and a small detent holds it shut
Tether
Optional 2 mm ear for a cord to the sensor body
Not for
Anything that needs an IP rating; we don't claim one
Price
€19 for two, fixed before we start
File
Download example STEP
Exploded along the cap's axis: the sensor's open well with its entry ledge and notch, then 3 the CR2032 cell, 2 the black O-ring and 1 the cap with its fluted rim, a lug and the O-ring groove, numbered as in the parts list.
Example design · exploded render
#PartQtySpec
1Battery cap2ASA, coin slot 2.2×17 mm, three-lug bayonet
2O-ring2NBR 70, 18×1.5 mm, bought
3Coin cell1CR2032, yours, not in the pack
Drawing at 4:1: a section of the cap in the well (a lug under the ledge, the O-ring on the bore, the CR2032 below, flange and bore diameters in red) and the cap from above with 36 flutes, the 2.2 × 17 mm coin slot and the lug tips dashed, their diameter in red to confirm.
Drawing · mm · red: to confirm on your bike · tap to open full size

Transport cover for an empty battery bay

A shell that locks into the bike's own battery lock, strapped and tethered, so the empty bay rides on the car rack closed.

Render of a clay-grey down tube, bike upside down on a stand, the empty bay closed by our black two-part cover: a blue-grey TPU lip round its edge, the lap step in the middle with three M4 button heads and CAR RACK ONLY · 1 Nm debossed, two black straps round the tube and a tether at the far end.
Example design · render
Fits
Bosch PowerTube bays 345, 416 and 484 mm long (500, 625, 750 Wh) and the PowerTube 800 at 424 mm; R&M Charger4 Mixte 1000 Wh and Nevo4 750 Wh, from a photo of the bay
Bolts to
The frame's own battery lock at the top, the battery's pivot pocket at the bottom, and two 25 mm hook-and-loop straps round the down tube as a second hold
Mass
206 g, CAD estimate
Material
ASA, 2.4 mm shell with 1.6 mm ribs; TPU 95A lip, 1.5 mm proud
Hardware
Over 256 mm long it prints in two pieces with a 30 mm lap joint: 4× M4 brass inserts, M4×8 ISO 7380 A2-70 button-head bolts
Torque
1 Nm on the four lap bolts, debossed on the cover
Tether
Ø2 mm cord from an ear on the cover round the down tube, crimped, so a cover that lets go stays with the bike
Not for
Riding, carrying a battery, bays without a key lock. It comes off before the battery goes back in and stays 8 mm clear of the contacts
Price
€49, fixed before we start
Exploded straight out of the bay: the two black segments lifted above it with the TPU lip frames between them and the tube, four brass inserts and four button-head bolts above the lap, the tether on the lower segment's ear and the two straps left round the tube, numbered as in the parts list.
Example design · exploded render
#PartQtySpec
1Lower segment1ASA, 2.4 mm shell
2Upper segment1ASA, 2.4 mm shell
3Lip2TPU 95A, 1.5 mm proud
4Heat-set insert4M4, brass, short
5Bolt4M4×8 ISO 7380 A2-70
6Tether1Ø2 mm cord, round the down tube
7Strap225 mm hook-and-loop with slide, 600 mm
Drawing in three views: a section along the bay (490 mm length in red, the 260 mm lower segment, the 30 mm lap, pivot pocket and frame lock), a cross-section of the cover on the D-shaped tube (R45 crown and 85 mm opening in red, 2.4 mm ASA shell, 1.5 mm TPU lip) and a detail of the hook with the 8 mm gap to the connector and the Ø3 drain.
Drawing · mm · red: to confirm on your bike · tap to open full size

Clips and guards copied from the surviving twin

Photograph the surviving one on squared paper, or post it to Warsaw, and we draw it, print it and keep the file for the next time. Twin still on the bike? Two photos of it in place with a ruler are enough to start; we mark anything else in red.

Render of a black clip hooked over a clay-grey section of the Urban Arrow box rim, a Ø10 rain-cover pole rising from its round socket and bending a little inwards.
Example design · render
Fits
Urban Arrow FamilyNext Rain Cover Plus clips, the Brompton G Line front-wheel hook guard, the Brompton P Line pedal-holder magnet carrier, frame cable-port grommets for shift and dropper housing
Bolts to
The same spot as the original: the EPP box rim, the hook, the pedal holder or the frame port. In the Urban Arrow example a 1.2 mm barb at each leg tip grips the EPP and the cover's pole drops into a socket
Mass
14 g each, this example, CAD estimate
Material
TPU 95A for clips and guards, ASA for hard parts, as the original
Hardware
Usually none; the Brompton carrier takes your magnet or a bought one of the same size
Not for
Brake housing guides and anything that carries load
Price
from €19, fixed before we start
Exploded straight up: 1 the black clip lifted off the rim with its socket bore in view, the end of the grey pole lifted above it.
Example design · exploded render
#PartQtySpec
1Rain-cover clip2TPU 95A, copied from your twin
Drawing at 2:1: a section across the rim through the socket (32 mm wall, legs 20 and 26 mm, a 1.2 mm barb, 3 mm TPU, 0.2 mm gap round the Ø10 pole, Ø3 drain) and the clip from outside, 34 mm long; values copied from the twin in red to confirm.
Drawing · mm · red: to confirm on your bike · tap to open full size

Also on request: a floor chock for a folded bike that won't stand on its own, shaped to its tyre. Parking only, for bikes up to 30 kg.

Fits

Bikes and devices we draw for

Sensors
Sigma BC 14.16 STS · Sigma BC 12.12 STS · Sigma STS Speed Transmitter 00541
E-bike batteries
Bosch PowerTube 500, 625, 750, 800 · R&M Charger4 Mixte 1000 Wh (send a photo of the bay: it may hold two batteries) · R&M Nevo4 750 Wh
Folding and cargo bikes
Urban Arrow FamilyNext with the Rain Cover Plus · Brompton P Line v2: pedal-holder magnet carrier · Brompton G Line, G Line Electric: front-wheel hook guard · Older Brompton: frame pump pegs · Tern Node D7i
Frames and cable ports
Scott Sub Comfort, Breezer Inversion Team 2021: cable guides for shift and dropper housing

Not listed? Send a photo.

Prices

Our price next to what's on sale

OptionPriceWhere it stops
Sigma STS Speed Transmitter 00541€29.95A whole sensor for one cap
R&M stock cover for the Nevo4 750 Whover €50One battery size; none for the 1000 Wh Charger4
Urban Arrow FamilyNext Rain Cover Plus€379A whole cover; we found no clips on their own in the catalogue (October 2026)
Brompton pedal holder Q103809via a dealerA whole holder for one magnet
Vincita A604 carbon protector for Brompton$12.90Sized for a 20 mm tube, held by 3M tape; G Line fit unproven
Neoprene, a mat or tape€0–15None of it is made to stay on at 130 km/h on a car rack
Ours: two STS caps€19Bayonet and O-ring, drawn from a photo of your well
Ours: a clip or guard from the twinfrom €19Copied from the surviving one; we keep the file for the next time
Ours: battery-bay cover€49Any PowerTube bay or the 1000 Wh R&M, under the bike's own lock, car rack only; we confirm your bike and bay before printing

Taxes included. Delivery is quoted with the part (delivery).

If it doesn't fit the bike and device we agreed on, you choose: a full refund or an improved part. If a measurement you gave us was wrong, we fix the design and the new part costs production only. This doesn't limit your statutory rights.

Riders' posts

What riders posted

From forums, not from customers

  • April 2026 Sigma BC 14.16 STS: the speed sensor's battery cap fell off, battery and all. The owner asked if the cap is sold alone, got an offer of a BC 12.12 cap that might or might not fit, and bought a whole new sensor.
  • September 2026 R&M Charger4 Mixte with a 1000 Wh battery. The down-tube cover is part of the battery, so on a car rack the empty bay rides open. Covers on sale fit the 750 Wh Charger only, and the stock Nevo4 cover costs over €50. Others use mats and neoprene. Bosch's advice is to take the battery off for rack transport.
  • October 2026 Urban Arrow FamilyNext: someone stole the front clips of the Rain Cover Plus. The owner had only an older, non-Next cover to compare, and a friend with a printer asked for the dimensions.
  • October 2026 Brompton P Line v2: the magnet fell out of the pedal holder mid-ride. The retailer's answer was a whole new holder, part Q103809.
  • October 2026 Brompton G Line Electric: the rider's plastic guard at the front-wheel hook broke after 8–10 commutes. It turned out to be shipping protection. Replies suggested a Vincita carbon protector.

12 posts, January to October 2026; folding bikes carry the most proprietary bits.

Limits

We don't make these: what to buy

We bolt to metal, to accessory threads, or where your radar's band sits today. We never make or modify brakes or steering parts, or anything that holds a rack or a child seat.

  • A derailleur hanger (Kross DP-75 and others) → The hanger for your frame from a Kross dealer, or from a shop list like Centrum Rowerowe's, where the Kross DP-69 costs 79,99 zł (99 zł list price)A hanger keeps the derailleur in line and is meant to bend before the frame does; a print would flex.
  • Shock bolts and bushings → RockShox mounting hardware, $15 per eyelet, in your eyelet width and bolt size (e.g. 30×8 mm), or the kit from your shock's makerThey carry the rear wheel's load.
  • A Tern handlepost strap → Tern's own strap, $6, or a Voile Nano strap, £6.50A bought strap does the job for less than a print.

We don't print parts clamped under a bottom-bracket cup, battery locks or rails, pedals, or guides for brake housing. Plastic under a cup creeps and loosens it, and a failed pedal, battery lock or brake guide hurts more than a lost cap.

Garmin, Varia, Wahoo, Hammerhead and other names are used only to say what a part fits. We're not affiliated with them.

Start here

Tell us your bike

Start with model names; we mark any measurement we still need in red. We reply within one working day, and if a shop sells a part that fits, we send you the link.

Tap what you have
Photos (optional, up to 3). The twin straight down on squared paper, or in place on the bike with a ruler.
What to send (optional)
  • Bike model and year, and what the part did
  • The surviving twin on squared paper, photographed straight down, or posted to us in Warsaw (we send it back)
  • If the twin is still on the bike: two photos of it in place with a ruler
  • If the twin is gone: a straight-down photo of the spot with a ruler, plus one caliper number
  • Cap: the well's diameter and the number of lugs
  • Cable port: length × width of the hole and the housing's outer diameter
  • Battery bay: its length, the width at three points and a photo of the lock bolt
Pictogram: a clip on squared paper next to a ruler, and a phone held straight above a part lying flat.
Or pick one:

The first ten bike orders ship free within the EU, and their photos go on this page if you agree.

Request sent.

We reply within one working day. If a shop sells a part that fits, we'll send you the link.

Send another request

Controller: Datar P.S.A., Warsaw. We use your request and photos to reply and quote and, if you order, to make and deliver your part (art. 6(1)(b) GDPR). They're stored by Cloudflare in the EU and reach our Google mailbox; we delete them 12 months after our last contact, or sooner on request. You can ask for access, correction or deletion, and complain to a data protection authority. Privacy policy · Terms.

FAQ

Questions before you order

Do you need the original part?

No, but the surviving twin is the best start: the other clip, the cap from a second sensor, the battery that sat in the bay. Photograph it straight down on squared paper and add one caliper number, or post it to Warsaw and we send it back with your part. Twin still on the bike? Two photos of it in place with a ruler are enough to start. If the twin is gone, a photo of the empty spot with a ruler does for a cap or a cable port. We mark in red any number we still need.

Is a printed cap waterproof?

It seals on a bought NBR O-ring in a groove, and the bayonet clicks into a detent so the cap holds its position. We print it in ASA, which copes with sun and with the sensor's −10 to 60 °C range. We don't claim an IP rating because we haven't tested for one. The pack has two caps and two O-rings, so the spare can ride in your saddle bag.

Will the bay cover stay on at motorway speed?

It's for car transport, under the bike's own lock, with two straps and a tether; we test it on a car rack at motorway speed before the first one ships. The lower end hooks into the battery's pivot pocket and the frame's key lock holds the top, the same way it holds the battery. At 130 km/h the wind lifts a 484 mm cover with 32 N by our estimate, so the straps are a second hold. Take it off before the battery goes back in. As of October 2026 these designs are drawn and rendered; photos of the first test prints will go on this page.

Can you make a derailleur hanger?

No. A hanger keeps the derailleur in line and is meant to bend before the frame or the derailleur does. It's aluminium for that reason, and a printed one would flex every time you shift. Ask a Kross dealer for the hanger by bike model and year, or find it in a shop's list: Centrum Rowerowe sells the Kross DP-69 for 79,99 zł (99 zł list price). Take the old one along to compare.

How long does one cap take?

We aim to send the first drawing within one working day of your photos. Once you approve it and pay, we aim to ship within 10 working days. If you post us the twin to measure, add the post both ways. We keep the file, so a second pair later on skips the drawing.

Other spots

The other five spots

01Radar or rear light under the saddlefrom €2902Computer on an integrated cockpit€5903Lamp under the bar€2904One bottle too fewfrom €2905Fork guards and rack partsfrom €19

All six spots →

Tell us your bike · free quote