Block and sheave constructed of rugged nylon fiberglass reinforced high dielectric material. Reinforced 1/2' diameter axle and swivel bearings. 3' sheaves - block can accommodate rope up to 5/8' diameter. Provided with either side opening or closed block. Blocks are rated with 3 - 1 safety factor. Working load limit 1,000 lbs. Weighs 1.8 lbs.