Shimano ultegra 6700 bottom bracket hollowtech ii integrated bottom bracket uses a wider bearing placement and larger axle diameter for increased stiffness and efficiency hollowtech ii integrated bottom bracket seal design has minimal bearing interface ensuring smooth rolling and increased durability 68mm threads 137 x 24tpi 70mm 136 x 24 tpi a 2 year warranty is offered with all shimano products from chain reaction cycles 3 years on dura ace and xtr products buy shimano components from