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This instructable will guide you through drawing a part in Autodesk 123D
, having it 3D printed, making a mold of the part, and casting the part in polyurethane rubber. I will gloss over some of the mold-making and casting since there are already so many good youtube videos on the subject.
The MuscleTreads™ water bottle massagers are polyurethane rubber rings made from Smooth On's Vytaflex® 60. They are designed to fit over a 1-liter SIGG bottle (or any bottle ~3.2" in diameter) to turn your water bottle into a back massager (used on the floor or against a wall or chair).
water bottle massagers are patent pending. You are welcome to make these for non-commercial use.
(This instructable has been updated to include instructions for how to make a one-part, open mold for this project. See Step 13.)