To figure out what size you need measure the circumference of your knee at the knee joint and compare your measurement to the sizing guide below

It's a seamless combination of form and function

14mm female axle w/ 9T driver

Whether you’re pushing pace on long road rides

Mountain biking & trail riding

S1 Lifer Helmet - Black Matte/Red Straps Color:Black To figure out what sizeThe S1 Lifer Helmet is one of the best fitting and safest helmets on the market. All S1 Lifer Helmets are manufactured with specially formulated EPS Fusion Foam which allows it to protect your head from multiple low force impacts as well as high impacts. The Lifer Helmet is a dual certified helmet and is up to 5x more protective than the soft foam non certified helmets. Whether you're riding your bike down the street or rolling at a local skatepark