Most Hobby RCs are of a professional grade, built to look like real cars, planes, and boats. Many hobby-grade RCs come as unassembled or partially assembled kits that you build from the group up. They are more durable to witshtand the bumps and crashes associated with high-speed racing and professional stunts. Because they are often build-your-own models, parts can be purchased separately and upgraded and customized more easily than toy grade RC vehicles. The more durable parts and the complexity of the construction incrase the manufacturing cost so hobby-grade RCs cost more to buy and to maintain.