Ronstan Series 55 Ball Bearing Orbit Block - Single - Becket - Swivel Head [RF55110]Series 55 Ball Bearing Orbit Block Single Becket Swivel Head Lightweight Kilogram for kilogram of working load, BB and RT Orbit Blocks are the world's lightest. The unique orbital design allows the bearing to only be in the active areas of the floating sheave. This minimises the mass of the inactive return race and hub. Weight and bulk are further reduced in the different block configurations. The ball bearing single and becket block has a through