Federal bbs sprocketthis cnc machined sprocket is made from 4130 chromoly and is heat treated for additional strength the central bore depth is 24mm which will fit straight onto federal cranks and any cranks with a 24mm spindle both 19mm and 22mm spindle adaptors are supplied which makes it compatible with most other crank models on the market features18 teeth4 5mm thick24mm bolt driveincludes 19mm and 22mm adaptors centre bore is 24mm diameter so will fit straight onto the federal crank