Polythene sheeting is a plastic film made from petroleum (you may also hear it referred to as polyethylene sheeting, poly sheeting, plastic sheeting, plastic film and poly film). It's an incredibly versatile product used in a wide range of applications.

The thickest plastic sheeting (not hard plastic but what is known as flexible plastic sheeting) is HDPE which goes up to 100 mil = 1/1000 inch. HDPE is a form of polyethylene that has a more compact molecule and has a higher density. HDPE comes in thicknesses of 12 mil, 20 mil, 30 mil, 80 mil, and 100 mil.

Not all plastic sheeting is waterproof. Of virgin resin, engineered plastic sheeting is waterproof! HOWEVER Construction and Agricultural grade sheeting (C&A), is not normally considered waterproof.