Holding tanks from Spin Products are made of durable polyethylene resin. They are available in black (graywater/wastewater) and white (potable/freshwater) in sizes from 5 to 250 gallons. Custom tanks can be made in any configuration to suit individual needs, with private labeling and custom colors available. Tooling is done in-house. 909/590-7000; www.spinproducts.com.