These blocks are works of art. Series 10 blocks have stainless cheeks and are engineered for high strength and high performance. They offer an oversized sheave system which employs multiple low-friction components. These are the blocks to have when you sail to remote locations, because the feature bolted construction so they can be easily disassembled for maintenance or parts replacement.
Line-only models come with Lexan sheaves and a friction-reducing, Teflon impregnated bushing

"UC" models feature high performance Universal Circuit Sheaves and incorporate an aluminum alloy sheave for high-tech lines or wire, low-friction Nomex/Teflon bushings and dual races of Delrin ball bearings
Easy spinning Nomex/Teflon bushing system impregnated with Teflon is immune to load-induced distortion, point loading or maintenance associated with roller bearings
Investment cast, three-way stainless head, forged "D" shackles
Sheave diameter: 3-1/4"
Pin diameter: 3/8"