Press-Fit BB use 24 mm axle and bearings, because 24 mm diameter axle and bearings offers the best balance of rotating performance, stiffness, strength, sealing, weight, for press-Fit type as well. Product features Use: MTB, Downhill, Freeride Model: SM-BB71-41C BB-Type: Press Fit BB107 (41x24mm) Press-Fit BB shell width: 104.5/107mm Shell diameter: 41mm Compatibility Saint FC-M825 ZEE FC-M645 Material Resin Weight 73g Scope of delivery Shimano Hollowtech II Press Fit Bottom Bracket SM-BB71-41C HOLLOWTECH II Technology The concept of HOLLOWTECH II technology is focused on producing a superior crankset which will maximize a rider’s power transfer. The rigidity of the crankset ensures pedaling efficiency while its weight, a key element of the crankset, you want light, aids in cycling longer distances over which the rider needs to pedal more. Naturally, SHIMANO strove for the optimum balance between the conflicting needs of stiffness while producing a lightweight crank. HOLLOWTECH technology is an ultra-lightweight hollow crankarm created by SHIMANO with the company’s own proprietary forging technology that also maintains rigidity. The addition of HOLLOWTECH II technology integrates the bottom bracket axle with the right crankarm for more stiffness and a weight savings to achieve a high-dimensional balance. Its outboard bottom bracket bearing system provides better weight distribution and more pedaling stability, allowing for more efficient power transfer.