EC30 will take a 38mm bearing EC34 will take a 41mm bearing ZS44 will take a 41mm bearing ZS49 will take a 41mm bearing EC44/40 will take a 52mm bearing EC44/33 will take a 47mm bearing EC49 will take a 52mm bearing ZS56 will take a 52mm bearing ZS62 will take a 52mm bearing IS41 will take a 41mm bearing IS42 will take a 42mm bearing IS52 will take a 52mm bearing All complete Cane Creek headset assemblies (top or bottom) will use a 36×45 degree contact angle bearing, with the exception of our IS47/33 and EC44/33 headset assemblies. IS47/33 and EC44/33 will use a 45×45 degree contact angle bearing.