A 45 lb rubber bumper plate (20.4 kg) is the heaviest standard increment in most bumper plate sets, used for deadlifts, squats, and Olympic lifting. These plates feature a 450 mm diameter (17.7 inches) to ensure consistent bar height from the floor across all weights. Virgin urethane models achieve 32-38 mm thickness for a 45 lb plate, while recycled crumb rubber versions measure 55-65 mm. The steel insert (50.4 mm inner diameter) fits standard Olympic barbell sleeves; anti-burst technology ensures slow deflation if punctured. For commercial gyms, 45 lb bumpers are typically purchased in pairs and color-coded: red for 25 kg (55 lbs) under IWF/IPF standards, but some manufacturers designate 45 lb plates in black or dark gray with printed weight labels. Weight tolerance varies by grade: competition (±15g), commercial (±1-2%), and economy (±2-3%). Buyers should verify insert retention (hexagonal or bolted designs resist spinning) and durometer (85-95 Shore A for dead bounce). A pair of 45 lb bumpers plus a 45 lb barbell totals 135 lbs, the standard starting load for deadlifts and squats in many training programs.