Designed for vangs, outhauls, shrouds where wire is used or for rope where loads are too high for regular bullet blocks. Roller bearings handle high loads better than ball bearings. Sheaves are aluminum for strength.Sheave: Teflon impregnated Hardkote anodized aluminumBearings: Delrin roller bearingsSheave Size: 1-1/8" (29mm)Line Dia.: 5/16" max.Cheek Material/Finish: Plastic with stainless strapBreaking Strength: 2000lb.SWL: 500