Built to stand the toughest of conditions, and still maintain their durability, these rollers are the ideal rollers, on the market today. Shaft Size 5/8" 11 gauge galvanized steel One-piece keel roller bracket with 5" slot for vertical adjustment Mounts with 1/2" bolt Designed to be used with a 5/8" roller shaft Tie Down&';s enhanced formula for PVC far outperforms traditional polyurethane products