Black Series alloy cranks are directionally CNC machined from grain orientated 7075 T6 heat-treated aluminium, with a CNC machined spider in 7022 aluminium featuring a universal 4-bolt 104/64 BCD Double bolt circle diameter. Extremely low weight and high strength. The integrated 30 mm diameter integrated hollow 7075 T6 heat-treated aluminium axle (fixed to the drive side arm) is a key feature of the cranks design, creating one of the torsionally stiffest systems on the market resulting in maximum power transfer, efficiency and silky smooth operation. This system is also the only of its type to fit practically all-current BB-standards through the use of frame specific BB cups (supplied separately) Supplied with Tune’s latest CNC machined 7075 T6 heat-treated aluminium Chainrings with hard anodised finish, the Black Series� Chainset is compatible with 9 & 10 speed groupsets. Each Chainring features a tooth profile, ramp and pin design compatible with Shimano & Sram systems. The perfect combination of form and function. A timeless design with classic lines, beautiful ball burnished & hand polished finish and laser-etched graphics. Proven in World Championship competition. Hand made in Germany by Tune.