Looking for your first Mountain bike and are ready to go on to the bike trails. Our Decathlon Rockrider ST100, 21 Speed Mountain Bike, 27.5", Unisex, Red, Medium is a great entry bike that is comfortable, durable, and safe. The Mountain Bike is designed for your first bike ride in dry weather for up to 1 hour and 30 minutes. Recommended Medium Bike height M: 5'5" - 5'9". With the bike's lightweight aluminum frame and 27.5'' tires on double-walled rims, you can easily get through any obstacle. The Mountain Bike has a total of 21 speeds, making it faster with smoother transitions and pedaling. Considering that you may need to transport or store your bike in a limited space (car trunk, porch, etc.), we have equipped it with a front-wheel quick release. The bike's rear-wheel has a fixing nut that reduces the risk of being stolen. To remove the rear wheel, you will need a wrench. Mountain Biking riding comfortably is crucial, the bike's frame position is raised having your back straight at all times. We offer a lifetime warranty on the Bikes frame, stem, and handlebar.