Groups of 2 to 6 sheaves in 4 diameters of 40, 50, 60 and 70 mm. Double version also available, just add D to the model number. The 40 and 50 mm sheaves are manufactured in high-strength resin with a double side ball bearing. The 60 and 70 mm sheaves are manufactured in aluminium, hard black anodized, with a main composite fibre bearing and 2 side ball bearings.