Measured in "mils" (1 mil = 1/1000 of an inch). "Thick" in this category usually refers to 6 mil to 10 mil material used for vapor barriers, construction covers, and tarps.
Measured in inches or millimeters. "Thick" here generally starts at 1/8" (3mm) and can go up to 1" or more . These are used for windows, machine guards, and structural building. 2. Choosing the Right Material buy thick plastic sheets
For custom sizes, specific engineering plastics (HDPE, UHMW), or thicknesses over 1/2": ePlastics Measured in "mils" (1 mil = 1/1000 of an inch)