Chooee Quick Release Skewers Front & Rear Set for Mountain Bike or Road Bike Superior Materials: These interlocking wheels are made of Cr-Mo steel and T-6061 aluminum alloy to ensure their durability and reliability. This powerful combination allows it to withstand a wide range of riding conditions, whether on city roads or rugged mountain trails. Quick Release Strings: These skeletal wheels are designed with a quick release feature that allows you to quickly change wheels when you need them, so you don't waste valuable riding time. Lightweight design: The front string weighs about 47g and the rear string weighs about 53g, which keeps the bike's lightweight performance and doesn't add extra burden. Size and weight: the front skewer weighs about 47g, the rear skewer weighs about 53g, the front skewer size is 100mm, the rear skewer size is 135mm, which maintains the lightweight performance of the bike and does not add extra burden.