Shimano FC-B124 is a front chainwheel with a BIOPACE chainring. It is designed to be used with a variety of bottom bracket spindles and front derailleurs. The chainwheel has a bolt circle diameter of 110mm for the large and middle gear, and 74mm for the small gear. It is recommended to use a front derailleur with a capacity of four teeth more than the difference between the number of teeth on the large gear and small gear of the front chainwheel.