Differences between Lg BU50N and Lg BU40N


Some sellers have BU50N in the short description seems having same specs of BU40N, but I haven’t found the full tech specs and in the Lg website is listed only BU40N. This Lg BU50N exists really or It’s some fake drive produced by others manufacturers.
If yes. Is there someone here that knows what is the difference between BU50N and BU40N?