A longboard is essentially a surfboard with wheels. Over time they have changed shape. They are most commonly used for cruising, downhill racing, slalom racing, or transportation. Longboards can be shaped in various different ways, depending on the type of riding intended. Their greater weight and bulk makes them less suitable for many skateboarding tricks, but contributes to a fluid motion by providing more momentum. Longboarding is often compared to surfing on concrete, and the design allows big turns or quick short carves similar to a surfboard.