Sizes available from 112-128 in 2 tooth increments. These are our most popular spur gears.They are made from high impact strength Delrin and are precision CNC machined. We cut our gear to instrument quality gear in order to produce not only the most accurate but quietest spur gear on the market today. They have 8 lightening holes with 12 outer diff holes and 6 inner holes that can be used to bolt on.