MJM's Exclusive Reinforced Caster System Allows Additional Structural Support To Our Entire Product Line - Our Positive Engaging Lock Holds The Wheel Securely So There Is No Swivel Movement When Locked * The Unique Design Allows Easy Movement On Hard Surfaces And Helps Eliminate the Wheel From Falling Into Cracks * Soft Non Marking Tread * (It Will Not Leave Black Marks Or Leave Groves In Wood Or Vinyl) * Quite Mobility * (Hard Treads Make A Lot Of Noise) Non Rust Plastic Body And Wheels * High Load Capacity (160 lbs). Non Slip Tread * Double The Tread Surface For Superior Breaking * Easy Reach Brake Tab * R-3TW 3 TWIN