Solid wheels are circular objects made from a single piece of material, such as rubber or plastic, without any air-filled cavities. They are designed to provide a sturdy and durable option for various applications, including bicycles, hand trucks, and industrial carts. Solid wheels are less prone to punctures and require less maintenance compared to traditional air-filled tires. These wheels offer a smooth ride on flat surfaces and are often used in environments where sharp objects might damage inflatable tires. However, they may not perform as well on uneven terrain, as they lack the cushioning effect provided by air-filled tires.