As if Kendall and Kylie mania hadn't reached peak levels already, (we're talking best-selling Lip Kits , countless campaigns and general world domination) the most influential sister duo on social media are adding another tier to their ever-expanding empire.Following on from two successful clothing collections with Topshop, which debuted last June, the pair have now designed an exclusive 37-piece swimwear collection with the highstreet megastore, just in time for summer, and each item is under £50. If you're one of their millions of followers on Snapchat you may have seen a teaser back in April when King Kylie previewed a yellow neon bikini emblazoned with their names on the band. (Just in case you didn't know who they were.)Launching tomorrow, 9th June, the new line is inspired by the Jenner sisters' LA lifestyle, with a range of bikinis, swimsuits and cover-ups. "We drew inspiration from our California roots," Kendall explains. "Every look captures the beach summer vibe of LA." Hey, if there's one thing these girls are pros at, it's poolside selfies, spending their fair share of time in bikinis and not much else.