Antal Mast Blocks are designed to be integrated into the mast for lines to pass through and down the mast. 12 different sizes with diameters from 40 to 140 mm for working loads (SWL) up to 9000 kg. Hard black anodized aluminium frame with insulating washers for corrosion protection. Resin sheaves (aluminium sheaves for 100, 120 and 140mm only) with composite fibre main bearing (not on size 40) and double side self-captive ball bearing.