Durable Material: The CE Smith Keel Roller is made from black natural rubber for long-lasting use Standard Fit: This boat trailer accessory fits standard brackets and shaft sizes for versatility High-Quality Trailer Accessory: Keel rollers are original equipment on many boat trailers for proper support Smooth Rolling: This boat trailer part is 3-1/2' in diameter and 11-3/4' wide for smooth rolling and proper support CE Smith Marine Accessories: CE Smith is committed to providing quality trailer and fishing products with responsive customer service