I don't think any of the replica (X300/X300U) are truly rated at 500 lumens. Only for RS X300U is rated at 500.
Pretty sure the replica are 300 lumens only, some sites listed misleading info, perhaps copied straight from Surefire site
Got my full trade X300 from Aliexpress for roughly $45 shipped. Would've picked up the Ultra instead if they were out
Go get yourself a DG switch from Surefire. Found one on ebay for $30 used. Pretty sweet