#50 chain sprockets are already bored to size and include a keyway and 2 setscrews. Our #50 finished bore sprockets are manufactured from 1045CD (Cold drawn) carbon steel, which is a higher grade than most sprockets on the market. Finished bore sprockets are commonly referred to as a "type B" or "type BS" sprocket. All sprocket teeth are hardened to minimize wear overtime and these are finished with a black oxide to help resist corrosion. Nitro™ 50 sprockets work with any #50 ANSI roller chain.