Pegasus 1800RNPNP54M 18' Round Newport Multi-Bead Liner for 54" Above Ground Pool. Liners are made from virgin vinyl, flexible Poly-Vinyl Chloride (PVC) sheeting containing various additives, i.e. inhibitors for mildew, mold and algae. These additives improve the life and quality of the vinyl by increasing its resistance to chemical/ detergents, brittleness, punctures, high strength with durability and low temperature flexibility.