Polyethylene (PE) is the material used over half of all films today, and low density polyethylene (LDPE) is the source of most poly bags. All of out stock bags are manufactured with LDPE for its great tensile strength, clarity, flexibility, and water barrier properties. It is also resistant to most caustic compounds.
For each layflat bag, there are three dimensions. The first measurement is the width across the opening of the bag. The length runs from the bag opening to the base of the bag. Gauge, the third figure in a bag's dimensions, is a measure of its thickness expressed in mils.
The width measures across the opening of the bag. The depth is the fully extended gusset. The length runs from the opening to the bottom, and the final dimension is the gauge (thickness).
When inspecting a bag keep in mind the polyethylene is a flexible material, and gauge can only be measured accurately with a poly micrometer. Machine micrometers, pinch and flatten bags or film. As gauge will vary across the width of any bag, ask your sales person for the appropriate weight of each case to be sure your bags are within tolerances.