3-ply foam liners are made of three layers: a thin foam core is sandwiched between two layers of LDPE film. 3-ply foam liner tends to be used interchangeably with foam liner. However, it actually performs better than a regular foam liner. Like the foam liner, this also does not create an airtight seal.
It is taste and odor resistant, and has a low moisture transmission rate, meaning it prevents moisture from entering the bottle and affecting product.