Ronstan Series 70 BB Orbit Block - Cheek RF75151Ball Bearing Orbit Blocks boast the highest strength to weight ratio available. This is achieved through all composite reinforced polymer materials and a Dyneema rope link head. Their precision design allows the optimum number of ball bearings in loaded areas and eliminates them in inactive areas. Ineffective mass is reduced even further through fibre reinforced composites in the block head, cleat arms and beckets. Specifications Sheave 70 mm Max.