the typical tlr is medium format, using 120 roll film with square images. presently, the chinese seagull camera is still in production along with lomography's lubitel, but in the past, many manufacturers made them. dhw-fototechnik gmbh, continues to make the rolleiflex tlr, as well. the ciro-flex produced by ciro cameras inc. rose dramatically in popularity due in large part to the inability to obtain the german rollei tlrs during world war ii. the ciro-flex was widely accessible, inexpensive, and produced high quality images. models with the mamiya, minolta and yashica brands are common on the used-camera market, and many other companies made tlrs that are now classics. the mamiya c series tlrs had interchangeable lenses, allowing focal lengths from 55 mm (wide angle) to 250 mm (telephoto) to be used. the bellows focusing of these models also allowed extreme closeups to be taken, something difficult or impossible with most tlrs. the simple, sturdy construction of many tlrs means they have tended to endure the years well. many low-end cameras used cheap shutters however, and the slow speeds on these often stick or are inaccurate.