Boat Roller Cotton Reel 6" (150mm) PolyurethaneA 6 inch (150 mm) cotton reel style boat trailer roller in durable polyurethane. Polyurethane rollers are significantly harder and more abrasion resistant than rubber while being gentler on hull gelcoat than hard plastic the ideal balance for fibreglass and aluminium hulls. The cotton reel profile provides a self centring contact surface that guides the keel and hull centreline evenly as the boat loads on or off the trailer.