Sea Dog Stainless Steel Chain StopperSea Dog Stainless Steel Chain Stoppers help prevent damage to your boat's windlass. These chain stoppers are for Sea-Dog and comparable bow rollers. They can mount alone or inside most bow rollers. Made of formed 304 stainless.Available Options:321820-1 Fits chain sizes 3/16" - 1/4"; 321825-1 Fits chain sizes 5/16" - 3/8";