It's a modular slingshot! It takes regular flat rubber bands, which can be found at any online retailer of your choice by simply searching for “slingshot flat rubber band”. I use the 1mm thick ones, but any size should work fine. 

It prints in parts, in order to be customizable with different grips, and to be printable on small printers with a 12x12cm bed, like the Voron Zero. The mating surface of the grip is symmetrical, so the side-grip can be mounted in both left-hand and right-hand configuration. Also allows you to easily design your own grip if you have an unusual hand size.

BOM: 

• M3 heat insert (4x)
• M3 x 8mm Socket Head Cap Screw (2x)
• M3 x 16mm Socket Head Cap Screw (2x)
   

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