Ronstans Orbit Blocks are ideal for sheet applications on dinghies up to 16' and control line applications for small keel boats. These blocks feature a precision, two-stage bearing for reduced friction under high loads.Sheave: Carbon fiber reinforced, PTFE impregnated engineered nylonBall bearings: High compression strength carbon black acetal; stage-2 bearing: glass fiber reinforced, MoS2 impregnated engineered nylonCheek material/finish: Toughened glass fiber reinforced nylon