What is PUL? PUL, otherwise known as polyurethane laminated fabric, is a lot more technical than just a plastic backing on fabric. The original application is the medical field, and it is still used for this purpose. Like cloth diapers, it is used to replace disposable products with reusable. It provides the waterproof barrier needed in the medical field that can survive multiple institutional washings. The laminate can also be autoclaved, which is a very high heat steam sterilization process, to make it safe for reuse even after it comes into contact with blood or other bodily fluids. The polyurethane laminate can be customized by the manufacturer and comes in different thicknesses. For cloth diapers, 1 mil or 2 mil is generally preferred. This allows for a good stretch, complete waterproofing, and is still comfortable enough to wear next to the skin. There are other options for waterproof fabric, but PUL is so durable and reliably waterproof it has become a favorite for cloth diapers. It has been truly kid tested! The solid color PUL fabric I sell is a thin 100% polyester knit fabric laminated with 1 or 2 mil of the polyurethane film. Although it's true that PUL fabric is non-biodegradable, it is still a better choice for the environment than disposable diapers.