Seldén 20mm Double - Ball Bearing (402-101-03R) is a 20 mm double-sheave ball-bearing block. It is intended for low-friction sheet and control-line systems on yachts, keelboats and dinghies. Stainless steel strap to ensure high strength and stiff sides. Stainless steel ball bearing races and glass fibre reinforced sheave for best bearing strength even under high dynamic loads. Glass fibre reinforced polyamide composite. Select the block by line diameter, working load and attachment style, and compare the article number when replacing existing Seldén hardware. For new installations, make sure the supporting eye, padeye or deck structure is suitable for the expected load and that the block can align naturally with the rope lead.