Ball bearing single sheave Orbit Block™. Requires 2 x 6mm (1/4") fasteners. VERSATILITY THROUGH STRENGTH The new Series 40 ball bearing Orbit Blocks™ provide the perfect balance of strength, performance, and reliability. They offer class-leading dynamic and static load ratings, the highest available in this size of performance blocks. Lightweight and strong toughened glass fibre reinforced nylon cheeks replace stainless steel straps used in traditional utility blocks - the perfect balance of performance and reliability. The sheave incorporate our 2-stage bearing system using ball bearings to minimise friction and a secondary full-contact bearing to maintain low friction across the full working load range. 2-stage ball bearing system. Fastener Ø: 6mm, Fastener Hole Centres: 30mm Applications: Mainsheet systems and spinnaker sheets on dinghies, off-the-beach catamarans and sportsboats to 8m (26ft). Halyard, vang and backstay applications on boats to 9m (30ft). Control line applications on larger yachts. Materials: BB Sheave and balls: High compression strength acetal. Frame/cheeks: Toughened, glass fibre reinforced nylon.