Amazfit Helio Strap / Whoop 4.0 Band Adapter

This adapter allows you to use Whoop 4.0 bands with the Amazfit Helio Strap. The Amazfit has a nice sensor but the straps are awful. The Whoop 4.0 had a great strap system, and the straps are still readily available. So, here you go, a fully 3D printable adapter - all you need is an Amazfit Helio Strap sensor, and a Whoop 4.0 Band (with the U bracket). Links below to compatible parts.

You'll need to remove the smaller metal piece from the end of the Whoop band, and thread the strap directly into the 3D printed case adapter (unfortunately, the Amazfit is a bit too long to work with that piece). To facilitate easy strap changes, just print a new case for each strap so you don't need to re-thread the strap all the time. Then pop the Amazfit into whichever you need. You can quickly switch between a Whoop strap and the OEM Amazfit straps as well if you want. 
 

Here are some Amazon affiliate links:

• Amazfit Helio Strap: https://amzn.to/45A6Cfr
• Whoop 4.0 Compatible 3rd Party Bands: https://amzn.to/41E7iPy

Printing notes:

• Either use a 0.2mm nozzle or set the ‘outer wall’ to 0.36mm. Print at 0.08mm layers or thinner. Some areas are quite thin.
• Print sideways, flat side down (dimple side up), with tree supports.
• Be careful removing the supports. I recommend flush cutters. The upper wall is thin and may break if you try to rip them off, depending on material (PLA+ can really stick sometimes)
• A small dimple is used to create the ‘snap’ closure. The closure will be pretty tight the first 5 or so times you open/close it. Then it should remain consistent. I tested this up to 100+ open/close cycles and it was very consistent after the first 5 or so times. If it eventually wears down… print another. It uses like 10 cents of material to print one of these.
• I printed in Polymaker Polymax PLA, but you might want something more temperature resistant. Probably would work great in Nylon. Note that the printed parts do not touch skin - only the bottom side of the Amazfit and the strap fabric touch skin. I still don't recommend printing in carbon fiber or glass fill filaments.
• Printed in the correct orientation, and once you put the Amazfit inside, it's pretty durable. Stronger than it looks
• If you are having any print issues the first recommendation is to slow it down (print on Silent).

Other notes:

• I am not affiliated with Whoop or Amazfit and have had no communication with either company. This is an unaffiliated fan-made accessory.
• Use at your own risk. If your 3D printed case randomly decides to explode and you lose your Amazfit and/or Whoop band, don't blame me.
• In case you're wondering, the Whoop 5.0 is too small - those U brackets won't work and I can't make a cast to fit them unfortunately.