Plunger

A plunger for a dispenser for cartridges containing materials to be dispensed, for example viscous materials, is disclosed, the plunger having three plunger portions which define empty spaces therebetween so that cartridges, for example two-component concentric cartridges, of a plurality of dimensions and configurations can operatively mate with the plunger. A dispenser having a plunger as described can be used with a multitude of different cartridge types, including concentric two component cartridges or cylindrical single component cartridges, of varying overall dimensions and configurations. Also disclosed is a plunger for assisting the alignment of a cartridge in the dispenser. Corresponding dispensers and methods of loading cartridges are further disclosed.