The Utility 4,000-X Composite TBR Trailer features a heavy duty Tall Bottom Rail (TBR) that is 10" taller and 50 percent thicker at floor level than the standard bottom rail, according to the company. The riveted bottom structural components, including an 8" wearband, are raised above the pallet rub, impact and work level and are replaced by an aluminum TBR designed to be smooth, solid and puncture-resistant.