Ronstan Series 55 Ratchet Orbit Block - Single - Swivel Head - Auto & Manual. Ronstan is the only company that offers a ratchet block with both auto and manual engagement modes. In the auto mode of the ratchet mechanism engages when load is applied but switches off when it's released. This lets the sheet run out smoothly and freely-great for rapid easing of the sheet and for gybing asymmetric spinnakers. In manual mode the ratchet mechanism can be switched on or off as required. This is the preferred mainsheet set-up for may top sailors. Try the block in both modes and see which you prefer - you really can't go wrong. Specifications for Ronstan Series 55 Ratchet Orbit Block: Manufacturer: Ronstan Color: Black Features of Ronstan Series 55 Ratchet Orbit Block Up to 20:1 holding powerSmooth easing of sheetsHigh performance cleatingSwivel shackle head for unlimited block rotation.Stainless steel shackle head for ultimate durability and compatibility with harsh fixing points.Automatic & manual ratchet block Applications: Mainsheet systems and spinnaker sheets on dinghies sportsboats and small keel boats to 8M(26')Halyard vang and backstay applications on boats to 8M(26')Spinnaker sheets on sportsboats and small keel boats (lateral lead blocks) Materials: Sheave: Hard anodised AluminiumBall Bearings: High compression strength carbon black AceetalFrame/Cheeks: Toughened glass fiber reinforced NylonRope Link: UV stabilized multi-strand impregnated SK75 DyneemaHead fitting: grade 316 stainless steel : Sheave : 55mm(2") Max. Rope : 10mm(1/2") M.W.L.: 250kg(550lbs) B. L.: 650kg(1430lbs) Weight: 82g(2.9oz) Package Contents: Ronstan Series 55 Ratchet Orbit Block Ronstan RF56100: Series 55 Ratchet Orbit Block - Single - Swivel Head - Auto & Manual