Steel canister in head is filled with shot and welded to handle rod. Entire hammer is encased in hot cast custom formulated Trucothane brand polyurethane. Trucothane is a custom formulation that eliminates mushrooming, splitting, absorption of liquids, contamination and chip pick up in faces. Trucothane outlasts rawhide, rubber, brass, lead, nylon and other plastic type heads by 10-20 times. Available with standard heads, slim-line heads with deep throats for specialized applications and sledge hammers.