4", Zinc, Heavy Strap Hinge, Exclusive Bearing Design Eliminates Metal To Metal Contact, Reduces Wear & Increased Life Expectancy By Up To 500%, Bearings Provide For Smooth, Quiet Operation & Remain Dimensionally & Structurally Sound In Hot & Cold Climates, Exceeds Strength Requirements Of ANSI/BHMA A156.20-1989, All Metal Parts Are Plated Prior To AssemblyTo Enhance Rust Resistance, 902 Zinc Plated Finish, Limited Lifetime Guarantee, Boxed Loose.