Though most car models are static display items, individual model builders have sometimes powered their vehicles in various ways, including rubber bands, springs, inertia mechanisms, electric motors, internal combustion engines, air engines and steam engines. In order to make them less fragile, powered models are often somewhat simplified and not as detailed as the best static models. For this reason, some modelers dismiss nearly all powered miniature cars as toys; however many individual efforts and commercial products are sufficiently well-scaled and detailed that they deserve to be called models. The main types of commercially produced powered car models include: