Series 30 Ball Bearing Orbit Block(TM) - DoubleBall Bearing Orbit Blocks(TM) 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 beckets.Features: Lightweight Highest working load in its class Secure, versatile and secure attachement Low profile and compact; Applications: Mainsheet systems and spinnaker sheets on dinghies to 5M(16') Halyard, vang and backstay applications on boats to 5M(16') Control line applications on larger yachts; Materials: Sheave: High compression strength carbon black Acetal Ball Bearings: High compression strength Acetal Frame/Cheeks: Toughened, glass fiber reinforced Nylon Link: UV stabilized, multi-strand impregnated SK75 Dyneema; Specifications:Sheave : 30mm(1-3/16")Max. Rope : 8mm(5/16")M.W.L.: 450kg(990lbs)B. L.: 900kg(1,980lbs)Weight: 50g(1.7oz) - cis2:mm5mnJlm -Quick Guide (pdf)