During my time working  at Tikkun Olam Makers (TOM), we developed a simple 3D printed prosthetic arm with interchanging add-ons  for different uses. The project is fully open-source, and all CAD files and assembly instructions were immediately uploaded to our website. The interest and demand led us to develop the Parametric Prosthetic app, which gives a broad solution  for size customization. With a click of a button, users can get a custom sized prosthetic arm which they can print and assemble easily, anywhere around the world.