Trevi 30324 21' Equinox Above Ground Pool Unibead Vinyl Liner use vinyls treated to resist UV rays to reduce the damage that can be caused by the sun and thus allow liners to survive the rigors of time, year after year. All of our vinyl covers are computer designed and manufactured at Trevi's Mirabel plant to exacting standards, ensuring a precise fit. In addition, we use the very latest assembly technology, which sets us apart from the competition.