10lb and 5lb weights are made from cast iron. Aluminum weights weigh 3lbs and has same dimensions of 10lb weight. Plastic weights weigh 1lb same size and shape of the 10lb weight. 10lb weights are 1" thick, 7" across the top, 4-3/4" across the bottom, 5/8" wide slot. 5lb weights are only 1/2" thick.