Some times I would like to attach a round rod directly to a motor shaft.This thing will accept a shaft of a specified size in one end, and allow you to attach to a 5mm motor shaft on the flat part of the disc. There is a M3 hole for a set screw to clamp on the motor shaft. There is no boss (something solid to hold the screw in place), so you have to be gentle when tightening.The default sizes are an 11mm "arm" and a 5mm motor shaft and M3 hole for the set screw.1) Print one of these 2) Insert whatever dowel or other shaft you're trying to hold into the large round hole that points out the side. 3) Press the disc onto your motor's 5mm shaft 4) Put an M3 screw into the hole on the side of the disc to hold tight to the shaft 5) Rejoice!You now have an "arm" that can be swung about by a motor.