You should be able to touch the ground with the tips of your toes when sitting in the saddle. To change the saddle height, bend your knee slightly and place your foot in the lowest position on the pedal. If you can't decide between two sizes, go for the larger one. The st 100 mountain bike frame is unisex, with a steep top tube slope and a wide variety of sizes (from xs: 1.45 m to xl: 2.00 m). A comment from our workforce this st 100 mountain bike was designed, developed, and assembled at our B'twin village in Lille, France. Mountain bikers, in particular, will enjoy it. Comfort, efficacy, and durability were top priorities for recreational mountain riders. Those attributes served as the foundation for designing, developing, and testing the st 100 mountain bike, which included real riders along the process. A-frame that is lightweight, comfortable, and fun on a mountain bike, finding the perfect position isn't always easy. Our designers have designed a completely new frame that is simple to step into. The CGF (comfort geometry frame) is made entirely of aluminum and is both pleasant and simple to use. The slope angle was created to keep your back straighter while the back was shortened to make the bike highly nimble when turning. Suspension in the front with the Sun tour 80 mm front suspension, you can confidently face your initial hurdles on mildly uneven trails. The pre-load adjuster on the fork allows you to easily raise or reduce the spring tension. Suspension in the rear: none there is no rear suspension on this mountain bike. This is a "semi-rigid" mountain bike, which is ideal for beginners embarking on their first mountain bike tours.