Harken Lead Rings are simple, weight-saving devices used to route line for jib in-haulers, twings, barberhaulers, lazy jacks, cascading backstays and other applications requiring minimal fine-tune adjustments. Rings are Hard Lube-anodized 6061-T6 aluminum for a smooth, slippery surface, and with no moving parts, wear is minimal.Center Hole Diameter: 8mm (5/16")Outer Groove Width: 5mm (3/16")Weight: 2.65g (.093oz.)