A mountain bike (MTB) or mountain bicycle is a bicycle designed for off-road cycling. Mountain bikes share some similarities with other bicycles, but incorporate features designed to enhance durability and performance in rough terrain, which makes them heavy. (although higher end mountain bikes may be lighter.) These typically include a suspension fork, large knobby tires, more durable wheels, more powerful brakes, straight, extra wide handlebars to improve balance and comfort over rough terrain, lower gear-ratios for climbing steep grades and sometimes rear suspension for a smoother ride on rough terrain as well as dropper-posts to quickly adjust the seat height.