Sheet film, sometimes known as cut film, comes in various sizes from 4x5 to 11x14 inches and larger. The most common sizes used are the 4x5 and 8x10 inch versions. Most sheet film doesn't have a paper backing and it must be loaded into and taken out of film holders in total darkness or under the proper safelight.
Some companies provide two sheets of film in a paper packet which can be loaded into packet film holders. Some packets are only available in the 4x5 inch format though. Most sheet films have reference notches in one of the film's edges. This is done so you can identify the emulsion side of the film and its type in the dark. Each film type has a different notch code. For sheet films that don't have the notches in them, the emulsion side of the film will have to be identified under a safelight. The emulsion side is a lighter than the base side of the film.
Color reversal film also comes in black and white, various speeds and costs about $80 for 50 sheets of 4x5 inch film.