Capsule intended for receiving a substance for preparing a beverage using a coffee machine or infusion machine, to be held by a piston during the passage of the extracting liquid after piercing of the base by the pins of the piston. The capsule made from injected plastic material has a base (1) and a side wall (3) together forming part of a frustrum of a cone, as well as a rim (4) covered by a lid (5) after the filling of the capsule with the substance. The side wall (2) is shaped as a single cone frustrum between the rim (3) and the open (12) base (1), formed as a flattened ring (11), connected to the side wall (2). The side wall (2) is covered by a label (23) and the open base (1), including the ring (11) thereof, is covered by a sealed lid (14) inside the base.