While they work well in virtually any genoa lead application, Scheafer's spring loaded genoa lead blocks really come into their own with unfair sheet leads. Due to their high degree of articulation, these blocks have the widest acceptance range of side-to-side sheet lead angle. Allow jib and genoa sheets to be sheeted at any angle, up to 45 to either side of the track 360 block rotation Heavy duty stand-up spring fully supports the block under all conditions Unique captive polyethylene liner on 1" and 1-1/4" models reduces sliding friction Stainless steel or black, hardcoat-anodized aluminum cheeks UV resistant Delrin sheaves The heavy duty model #10-92-UC features Schaefer's aluminum Universal Circuit sheave which combines a low friction Teflon-impregnated Nomex bearing with Delrin 107 ball bearings and is precision engineered to withstand heavy static loads, yet still run free on the ball bearings when lightly loaded