Ballast added to the tractor or implement to improve balance, traction, stability or digging force. Tractor weights include calcium solution in the tires (usually rear only) to improve traction and/or balance when using a loader, suitcase weights -- slabs of iron held together by a U-shaped bolt and attached to the tractor frame, wheel weights -- circular or semi-circular slabs of iron secured by the wheel lugs, and a weight box -- a rigid box attached to the rear of the tractor, filled with small stones or wet sand, to improve balance when using a loader. Implement weights include sand bags, cement blocks, large rocks, etc.