Ronstans high-performance Series 55 Orbit BB Blocks incorporate unique bearing systems, super light, all-composite materials, innovative head fittings and a sleek design for the highest strength-to-weight ratio available. Precision design provides the optimum number of ball bearings in critically loaded areas, eliminates them in inactive areas and reduces ineffective mass, creating the 2-stage bearing system for durability and low-friction performance. The use of a flexible Dyneema rope link is a product of trends in grand prix ocean racing and provides a more flexible, lighter weight and lower-profile solution than traditional shackles. It can be set at a 0- or 90-degree orientation, provides stress-free articulation without allowing the block to over-rotate, and is locked in place with a security clip that doesnt require tools to fit.Sheave: Carbon-fiber reinforced, PTFE-impregnated engineered nylonBearings: High-compression–strength carbon black acetal; Stage 2 bearing: Glass fiber-reinforced, MoS2-impregnated engineered nylonCheek material/finish: Toughened glass fiber-reinforced nylon