Check the listing for details. 57mm Aluminium Fork-Head Block with 8mm Pin - Master ALC-5729F. Condition: Brand New. Listed at 86.41 USD. product specifications 57mm Aluminium Fork-Head Block with 8mm Pin - Master ALC-5729F Sheave diametre 57 mm Sheave diametre 2 1/4 in Maximum line diametre 12 mm Maximum line diametre 1/2 in MWL / BL 750 / 1500 kg MWL / BL 1653 / 3307 lb product range - alc blocks Master ALC blocks are available in 57mm and 75mm sizes and several configurations. They are designed for larger cruisers or racers providing efficiency and durability in high-load applications. The range features: a Delrin sheave with self-lubricating bushing rotating on a 316L SS shaft for limited friction and high static loads,Delrin ball bearings to manage side-loads and for efficiency,side plates in either; hard-coat anodized 6061-T6 aluminium or hand-polished 316L stainless steel which will not distort under high-loads.where applicable blocks are topped with a highly polished 316L SS shackle and feature Master’s patented locking mechanism.