UHMW Polymer (plastic) is a linear polyethylene with a molecular weight in the range of 3,000,000 to 6,000,000. This value represents the "average molecular weight". UHMW is 10 times heavier than regular high density polyethylene. Please note: the size of each piece will vary slightly due to the kerf of the saw cut. In most cases it will be slightly under the 4" x 48" measurement.