Mate off the top off my head DID dont do just a 50VX chain they do a 50(530)VX!
They do 520, 525 or 530 you want 530VX or heavy duty 530ZVM-X, there are loads and I mean loads of cheap crap Chinese copies that some stealers and ebay sellers are passing off for genuine DID/RK/IZUMI etc. Make sure what you bought both chain and link are genuine, personally I only buy from official dealers of DID you can find your nearest by giving Maxxis a call.