Product DescriptionSpecifically designed with the needs of mountain biking and BMX in mind. These pads are meant to take the beating from your bike so your shins/calves dont have to. To ensure a perfect fit measure the circumference of your calf where your muscle is thickest Small – 13-14 Inches Medium – 14-15 Inches Large – 15-16 InchesFrom the ManufacturerSpecifically designed with the needs of mountain biking and BMX in mind. These pads are meant to take the beating from your bike so your shins/calves dont have to. To ensure a perfect fit measure the circumference of your calf where your muscle is thickest Small – 13-14 Inches Medium – 14-15 Inches Large – 15-16 Inches.