Security Brands K-CRPR6 Cantilever Round Gate-Frame Roller. Roller fit 2-3/8 inch (2.375 inches in diameter) round gate frames and secure to 4 inch round (diameter) posts/stocks. Comes with fastening hardware and protective covers. For larger, commercial- grade sliding/barn-style doors, they have zinc-plated axles and rollers crafted from graphite-impregnated wheels of UHMW polyethylene, a polymer often used in marine-grade applications so you know it will keep rolling. New from North Shore Commercial Door. Order today!