The TRACE Short Style Softball Knee Guard is a single protective pad that provides excellent protection when fielding and sliding. It features premium 3/8 inch vinyl/ nitrile foam that is engineered to minimize compression set. The patented “keyhole” design on the side allow for superior flexibility. The spandex/polyester fabric provides additional comfort. The pad is machine washable. Measure calf area of leg for a correct fit: SMALL - 8.75 inch pad length, fits 10.5 inch thigh circumference and 8.0 inch calf circumference. MEDIUM - 9.0 inch pad length, fits 12.0 inch thigh circumference and 9.5 inch calf circumference. LARGE - 9.75 inch pad length, fits 13.5 inch thigh circumference and 10.5 inch calf circumference. X-LARGE - 10.25 inch pad length, fits 14.5 inch thigh circumference and 11.0 inch calf circumference. XX-LARGE - 10.75 inch pad length, fits 16.0 inch thigh circumference and 11.0 inch calf circumference.