Ronstan Series 30 Ball Bearing Orbit Block - Single - Becket - Swivel Shackle HeadSeries 30 Ball Bearing Orbit Block Single Becket Swivel Shackle Head Ball Bearing Orbit Blocks boast the highest strength to weight ratio available. This is achieved through all composite reinforced polymer materials and multiple attachment options. Their precision design provides the optimum number of ball bearings for minimum friction while weight reduction is achieved through the use of fiber reinforced composites in the block head, cleat arms and