【Material】This side guide roller is made of high grade molded rubber, resisting oil, fuel and salt corrosion. 【Size】This boat trailer roller is 12 inches long and 2-1/2 inches in diameter, with ID 0.75 inch hole. 【Installation】This side guide roller fits standard brackets and shaft sizes, easily mounting to the same bracket as the trailer roller. 【Function】This boat trailer roller is designed to absorb the shock of launching, loading, and hitching, easing loading and unloading of your boat onto the trailer. Boat Trailer Black Molded Rubber Side Guide Roller