Non-sterile and disposable covers prevents cross-contamination. 2 mil polyethylene is transparent to x-ray. Keeps receptors clean and dry from exposure to urine, feces, blood, and other bodily fluids etc. Perfect for up to 14 x 17 receptors. Bag size is 17.5″ x 20.5″ with an Ziplock closure. 500 bags per box.