Question: what is gxp bottom bracket?
Answer: SRAM GXP cranks have a spindle with 24mm diameter on the drive side and 22mm on the non-drive side. Using a GXP crank means that you also have to use GXP (compatible) bottom bracket bearings. The different SRAM GXP bottom bracket bearings. Besides these, SRAM also has BB30 cranks with a 30mm spindle.