All the B5s were transferring to Consett for the 16/16A, leaving 4 free. Had to put them somewhere and the X5/X15 had that correct PVR for them. I see no other logical reason why 6301-6304 were taken off other than that. In reality why they made the 15/15A into the X5/X15 and upgraded to Xlines i dont really understand, for that matter why the added X to the 45/46/47 when there's no difference to route, albeit non stop between Metrocentre and Newcastle.