For attaching the inner and outer chainring Compatibility: Single 4-arm chainrings. Thread: M 8.5 x 0.75. Thread length: 4.5 mm. Sleeve length: 4.7 mm. Tool fitting: 4 mm hexagon socket (screw), 4 mm hexagon socket (nut). Material: anodized steel.
Best Price: £30.00 from Merlin Cycles