Precision internal gears from Quality Transmission Components are stocked in 22 sizes in modules 1 through 3. These 20^o pressure angle internal gears, identified as the SI and SIR Series, are made from S45C steel which are black oxide coated and have tooth hardness less than 194HB. They can be combined with available spur gears to make planetary gear drives. Both Series can be cut to make segment gears or corner racks. The SI Series conforms to JIS N8 grade, and the SIR Series conforms to JIS N9 grade standards.