Prime threaded bottom bracket shimanodesigned for use with all shimano and fsa cranksets with a 24mm axle diameter, prime's threaded bb is a high quality bottom bracket. Precision made for durability and smoothness prime bottom brackets keep your bike running smoother for longer.low friction bottom bracketdesigned so that the bearings rest on the axle of the crank, these bbs provide a straight load to the bearings, which means your bb will last longer. This also allows us to make the prime threaded bb with tighter tolerances, so it runs smoother with less friction. This means you'll require less effort to make it up that hill or sprint for the line.to keep our threaded bb running smoother for longer, we use special seals that keep water out of the bearings. We use multiple smaller seals, which reduces friction and provides a better barrier against moisture and dirt. Our bearings themselves are manufactured to precision and packed with slick, waterproof grease.all of the above combine to make the prime threaded bottom bracket the ideal choice for riders who want the best from their bike components.please note bsa ita options available, so please ensure you select the correct item from the drop down.features bearing premium stainless steel frame type bsa or italian threaded crank type shimano fsa 24mm compatibility compatible with 68mm road bb shells installation shimano tl fc24 bottom bracket tool adaptor required to install weight 69gbuy prime components from chain reaction cycles, the world's largest online bike store.