Luvari Liners LA5RO2100BL4ST 21' Round Blue Streamstone Overlap Above Ground Liner 48"/52" are true multi-taskers, keeping water securely inside your pool while providing a smooth surface for scrape-free swimming. From preventing injuries to maintaining proper structure, pool liners play an essential role in minimizing maintenance and maximizing enjoyment. with our patented Ultra-Seam technology, which comes standard on all of our pool liners, you’ll never see an unsightly seam again.