A Simplex Center Slitter/Rewinder winds a roll on a single shaft in a similar way to a Two Drum Winder. Unlike the two drum, however, the Simplex rewind shaft grabs the core or cores usually by inflating the rewind shaft with air. The air causes an internal bladder to expand thereby pressing buttons or the leaves of the shaft itself inside the core. The secured core is then driven to wind the roll from the center. Usually the roll runs against a nip roller which helps remove entrapped air and induce tension. Sometimes this nip roll can be driven, or a small gap between this roll and the material being rewound can be maintained, creating the so called minimum gap. Normally these winders are used for paper or other materials which are not extensible and have a good profile. A great advantage over any type of duplex winder is the ease with which the shaft can be unloaded and restarted.