40mm Single Tii-On Block With High Load Sheave.The 40mm single tii-on block is our go-to dinghy mainsheet block. Also ideal for dinghy jib and spinnaker sheeting systems as well as keelboat control lines.Our Tii-On blocks feature a stainless-steel loop at the head of the block. This gives our Tii-On range maximum strength and reliability with minimal cheek separation when tied on and loaded up with a soft shackle. The stainless-steel head loop also ensures the block stays in the right orientation when being used.When attaching a Tii-on block you must feed the rope around the central axle and through the head of the block. Tii-On blocks rely on the correct attachment method to give them maximum strength.High Load Sheave - High load blocks feature a stainless-steel sheave. This upgrade offers even faster rolling speeds and lower friction when compared to the standard acetal sheave. The stainless-steel sheave allows the block to be paired with both rope and wire.Becket Ð The large central rivet not only reduces the overall weight but also offers a rope friendly attachment, perfect as a tie-off point when being used in a cascade system.Bearings Ð Dynamic Blocks feature our patented bearing system which uses twin rows of stainless-steel ball bearings running on a stainless-steel rail. This provides a superior load-carrying ability and longevity when compared to other bearing systems which run on a plastic rail.