20 teeth metal gear, properly crafted, sturdy and durable, immune to high pressure, blackened, non rusting, and non deformation. The tools with a 5mm hole is suitable for the 775 motor shaft. There is a threaded solving hole on the aspect for putting in the screw fastening shaft, with a gap diameter of 3mm, using M3 screws.(1) Module: 0.5M(2) Inner hole: 3mm, 4mm, 5mm, 6mm holes(3) Thickness: about 10mm(4) Tooth floor width:about 5mm(5) Gear outer diameter:about 11mm(6) Material: Iron containing carbon metal