Lenovo on Twitter: "Hi! Thanks for reaching out. Good question, based on the parts listed in this article https://t.co/VsRcGVhGgI page 66 the Legion Y520 uses M.2 NVMe SSD. Kindly check this link
lenovo legion y520 gaming i7 7700HQ, GTX 1050 in B15 Birmingham for £500.00 for sale | Shpock