Google just made its $99 Fitbit Air tracker a lot more appealing to DIY enthusiasts. The company released official design guidelines that include exact dimensions, tolerance margins, and 2D CAD files in PDF format, giving makers everything they need to 3D-print custom bands and accessories at home.

The Fitbit Air splits into two parts: a "pebble" holding the sensors, battery, and core electronics, plus a "sleeve" that wraps around it and connects to the bands. Google's documentation specifies precise mating dimensions, attach and detach force tolerances, and clearance requirements so that the heart rate and SpO2 sensors stay unobstructed.

Google also recommends using skin-friendly materials and maintaining consistent contact between the tracker and your wrist for accurate readings. By publishing these specs openly, Google is inviting a community of custom accessory makers rather than locking users into first-party bands. That is a notable shift for a fitness tracker at this price point.