Keep cold air inside and hot air out. Quality and Wearproof: the vinyl strip curtain is made of heavy-duty impact-resistant PVC, which is smooth, waterproof and UV-proof; Its special formula stays flexible down to -20F (-29C) (no brittleness or cracking even in cold storage), unlike regular vinyl; Anti-static surface prevents sticking for clean separation and a tight thermal seal, while scratch, wear and wind resistance ensure long-lasting performance in harsh conditions.