The invention includes a piston having a piston body (1) and front seal for sealing the gap between the side wall of the piston body and the wall of a chamber within which the piston and a material are disposed in a conventional manner. The front seal (5) has a leading edge (6) included angle (A) as defined below, and a trailing edge (7) included angle (B) that is smaller than the leading edge included angle. By the appropriate selection of these two angles, the force required to move the piston (and thus the material) is optimized, the force required to move the piston (and thus the material) is optimized, which results in a more useful dispenser than conventional syringe-type dispensers. These and other features of the present invention are described in greater detail below.