Essential Data Plate diameter: 450mm (IWF Standard is 450mm) Collar opening: 50.40mm* Insert type: Steel disc, zinc plated Weight tolerance: +/- 10 grams of claimed weight Coloring: A (graded: A through F) Odor: Low Classification: High Grade Bumper Plate Material: Virgin Rubber and Rubber Additives Origin: Made in China, Printed in South Carolina *MuscleDriver USA only guarantees that bumpers plates will fit properly on Pendlay Bars, York Bars, Rogue Bars and all IWF certified bars. Low end bars are not manufactured with strict tolerances for the collar diameter. Collar diameter for quality bars is in the range of 49.70mm-50mm. Pendlay Bars are an exact 50mm which conforms with IWF requirements.