Abstract: A drum used as a clamping roller for mounting a substrate, such as a sheet of paper, in a device in which the surface of said substrate is treated.The clamping roller is of use in a device such as an electrojet printer. The roller comprises a thin metal seamless sleeve having perforations; a coating is present on the sleeve having such form that a great variety of substrate formats may be held on the roller surface by creating a low vacuum inside the sleeve.For all formats the coating is of similar form.The thin sleeve is centered around the roller's axis by means of centering means having the form of end-discs.