Foamed polyethylene (F217)
Commonly used with plastic screw caps. F-217 is a soft polyethylene foam core covered on top and bottom with solid, clear polyethylene supplied in 0.050 inch thickness. F217 has become the industry standard due to its all purpose compatibility, resilient, compressible seal, cleanliness (no pulp dust) and economy. F217 liners have excellent chemical resistance and a low moisture transmission rate. F217 has good taste and odor resistance.

Plastiso
Plastisol is the standard lining material used in metal closures for vacuum packing glass bottles and jars. Plastisol is a flowed-in compound, usually a dispersion of PVC resins in plasticizers. It forms a solid, self-bonding, sealing gasket in the closures. Plastisol liners are used in metal twist-off and metal continuous thread screw caps for use on hot-pack food products where the preservation of a vacuum is essential.

Pressure-sensitive liners
Styrene foam material coated on the down facing side with torque-activated adhesive. Pressure-sensitive inner seals adhere to plastic or glass bottles with normal application torque. Pressures sensitive liners are supplied pressed into closures and adhere to the bottle finish when the closure is applied. Pressure-sensitive liners stick to the container because one side is coated with pockets of adhesive. When the closure is applied to the container, the pockets of adhesive rupture between the closure and finish of bottle or jar. The pressure-sensitive liners then stick to the bottle or jar and remain in place when the closure is removed. No extra equipment is required. The closures are supplied with a standard liner as a backing. This material needs a dry land area on the bottle and therefore is suitable only for use with dry products such as vitamins, foods and pharmaceuticals.

Polyseal cone liners
Molded in Low Density Polyethylene, Polyseal cone liners form to the inside of the bottle neck providing a leakproof seal which guards against back-off and product evaporation. Excellent for use with acid products and essential oils, these closures are recommended for use on glass bottles only.