1200 denier nylon outer skin^ EVA foam padding^ PP proctective shells^ Adjustable velcro straps * Super Durable 1200 Denier Nylon Outer Skin; Comfortable 12, 14 & 18mm EVA Foam Padding; High-Impact PP Protective Shells And Splint; Adjustable Velcro Straps; Open Back Knee Pad Design Allows You To Put Pads On Without Taking Off Shoes * Sizing Chart: XSmall = under 4"6 inches; Small = 4" 6 inches - 5"; Medium = 5" - 5"6 inches; Large = 5"7 inches - 6"; XLarge = 6"+ * Pads should fit tight and not move around during a fall.