Our 35BS12H sprocket is an ANSI standard sprocket with a 1/2" finished bore that has 2 setscrews and no keyway. This sprocket is available with a keyway here. 35BS12 sprockets are a 12 tooth sprocket that works with ANSI #35 roller chain. These sprockets are manufactured from 1045CD carbon steel material. The sprocket teeth are hardened for increased wear resistance.