All-mountain SLX Hollow Tech II chainset is tough & aggressive yet also lightweight & excellent value The Hollow Tech II Chainset features hollow forged crank arms which are both lightweight & rigid whilst being incredibly strong & durable Hollow Tech II integrated bottom bracket design uses a wide bearing placement with a large axle diameter for increased stiffness&44; efficiency & added durability Double version comes with a honeycomb style bash guard which has been developed to absorb impacts Triple version comes with a drilled steel & carbon composite construction middle ring for excellent rigidity & durability Mega 9 HG chainrings for optimum shifting performance SG-X chainring with patented spike pins give smooth & fast gear shifts under load We recommend that the bottom bracket is initially installed by a bike shop to ensure perfect facing & fit Two tone anodized finish for long lasting good looks Available as FC-M660 triple: 44/32/22 tooth or FC-M665 double with bash guard: 36/22 tooth Comes complete with bottom bracket for 68 & 73 mm frames