Bumper Plate Pair of 5 KG. The thikness of 5 KG Bumper Plate is 25 mm. 2 PCs of 5 KG Bumper Plates inside the package. Each bumper plate has an inner ring with a diamter of 2" and fits any olympic barbell, dumbbell bar or sled with a 2" diameter. NOTE: 5 KG bumper plates are not designed to be used alone on a barbell. IMPORTANT - 5 KG plates can bend when dropped ALONE while on a barbell.