26-inch wheels are a common size used in various types of bicycles, including mountain bikes and some hybrid models. This size refers to the diameter of the wheel, which can affect the bike's performance, handling, and comfort. These wheels provide a good balance between speed and stability, making them suitable for both off-road and on-road cycling. They are often favored by riders who enjoy a mix of terrains, as they can handle bumps and obstacles effectively while still allowing for a smooth ride on flat surfaces.