BMX Racing COGs and FreeWheels.
COGs - Shimano cassette compatible.
Freewheels - Thread: 1.181" x 25.4 TPI (Ø interne : 30mm - 13-15T) - 1.375" x 24 TPI (Ø interne : 34.92mm - 16-22T)
Compatibility - Chains: 1/2" x 3/32"
From 12 to 22 teeth.