These refills for the BootieButler's automatic shoe cover dispensers completely waterproof and are anti-skid. Each cover is made of spunbond polypropylene material with non-skid, non-conductive soles that a durable for extra-long wear time. The tops have a strong elastic band that allows for a one-size fits most that fits up to a men's size 15 shoe. The shoe covers come in bundles of 40 pairs, with 15 bundles in a case (totaling 600 pairs). Approved for Class 100 & Class 5 cleanroom use per federal standard 209E and ISO STD. 14664-1 Class 5.