Rear lens caps · AirTag
Canon EF rear cap with an AirTag inside
A Canon EF / EF-S rear cap with an Apple AirTag hidden in its base. The tag snaps in from the inside and stays out of sight, so a lens left on set or in a rental case shows up in Find My.
One part, no screws
Three snap tabs, 1.2 mm thick with chamfered roots, stand up from the face and hold the AirTag by its widest point. Press it in from the inside until it clicks; a notch between two tabs lets you lift it out again with a fingernail.
Signal side out
The white side of the AirTag faces outwards behind a 1.2 mm face; the steel cover faces the lens. The lens keeps its full rear room.
Prints without supports
Every tab grows from the layer below, nothing is printed in mid-air. Face down on the plate like every Focus Rings cap.
Same bayonet
Three claws sit in the lens neck like a camera bayonet. Put the lugs into the gaps and turn clockwise (looking at the face): after 34° each lug runs onto a stop. The AirTag adds 7.3 mm of height and leaves the lens room unchanged.
Fits
- Canon EF lenses (full frame)
- Canon EF-S lenses, whose rear element sits deeper
- Third-party EF-mount lenses from Sigma, Tamron, Tokina, Samyang and others
| Mount | Canon EF / EF-S |
|---|---|
| Outside diameter | Ø63.2 mm |
| Height | 24.0 mm |
| Room for the rear element | 14 mm below the rim, enough for EF-S rear elements |
| Grip | Module 0.8 gear (77 teeth) or flutes |
| AirTag | Apple AirTag, snap-in from the inside, no tools |
| Print orientation | Face down, no supports |
| Print time (slicer estimate) | about 56 min, about 21 g |
| Fit test ring | Free, about 15 min |
| Files | 3MF (body + face inlay as one object), aligned STLs, printing guide |
Print times are Bambu Studio estimates for an X1C with a 0.4 mm nozzle and 0.20 mm layers. Not every lens has been tested: print the free fit test ring first.
Print and fit
- Print the free fit test ring in the generator. It is the bayonet zone only and done in minutes.
- Put the lens lugs into the gaps and turn clockwise (looking at the face) until it stops. It should turn smoothly and sit firmly.
- Print the cap face down on the build plate, no supports. Two-colour faces: keep body and inlay as one object and give each part a filament.
- Press the AirTag in from the inside, white side towards the face, until the three tabs click.
Questions
How is the AirTag held without screws or glue?
By three snap tabs that flex slightly as the AirTag passes them, then rest over its widest point. If the click is too stiff or too loose on your printer, write to us and we send a different nub size.
Does the AirTag still work inside the cap?
AirTags work through plastic, and the white side faces outwards behind a thin face. Range depends on what is around the lens case, as with any AirTag.
Which lenses does the Canon EF AirTag cap fit?
Canon EF lenses (full frame); Canon EF-S lenses, whose rear element sits deeper; Third-party EF-mount lenses from Sigma, Tamron, Tokina, Samyang and others. Room for the rear element: 14 mm below the rim, enough for EF-S rear elements.
Has this Canon EF rear cap been tested on a lens?
The bayonet is measured from caps that fit real lenses, and every file passes a layer-by-layer support check. Printers and filaments differ, so print the free fit test ring first: it is the bayonet zone only, done in minutes, and shows on your lens whether the cap will turn on and lock.
Does it need supports?
No. The cap prints face down on the build plate. Every overhang is at most 50°, and the claws have sloped undersides that build up layer by layer.
Which filament should I use?
Rings without clamps and lens caps: PLA or PETG, 0.4 mm nozzle, 0.20 mm layers, your usual walls. PETG is a little tougher if the cap lives in a bag.
Why gear teeth on a rear cap?
They are the same module 0.8 teeth as our focus rings, so the cap matches your follow focus gear and grips well with gloves. The vertical teeth also hide layer lines. Prefer something smoother? Pick the flutes grip.