Quite simply, Ronstan Ratchet Orbit Blocks™ have the highest holding power available. The sophisticated NC-machined sheave features Generation 2 of our patented sheave cross-hole geometry. The Series 40 delivers up to 14:1 holding power, almost double that of our nearest competititor. The unique sheave design has 8 gripping faces which directly resist loaded line movement. Traditional designs have an angled resistance to line movement. Our Generation 2 design has straight resistance faces which both distribute the load and minimise rope wear. These faces are offset from the radial line, to draw the rope down into the gripping area when under load. With the automatic models, the ratchet mechanism engages when load is applied, but switches off when it's released. This lets the sheet run out smoothly and freely which is great for rapid easing of the sheet and for gybing asymmetric spinnakers.