Grow1 PE Grow Bags are a great alternative to expensive pots. Grow1 PE Grow Bags are 5.5mil thick and are made of strong polyethylene. All black bags are perfect for blocking light and help with algae, mildew, and pest control. White and black bags feature an all black interior as well as an all white exterior to help reflect light. All Grow1 PE Grow Bags feature prefabricated holes to assist with drainage.