Abstract: An exercise mine has a ballast portion, a generally barrel-shaped body constituted by a single piece molded about the ballast portion and a plurality of U-shaped metal fitting members having terminal portions that form resilient tabs which project outside the periphery of the body. The fitting members are secured together in groups to permit, along with the single molded body, the mine to be readily formed from just a few parts while ensuring the mechanical strength and durability of the mine.