The SRAM BB30 Crankset Spacer is a 2. 5mm spacer that goes on 30mm crank spindles, on each side of the bottom bracket, between the crank arm and the bottom bracket bearing shield. The spacers take up the 5mm nominal difference between 73 and 68mm shells on PF30 and BB30 frames for proper chainline and bearing preload. Includes 2 x 2. 5mm spacers.