Doesn't fit properly. - Vism BlastAR Handguard Carbine Extended

The item says it fits on carbine length rifles, however the inner rails on the top piece are too long to fit on my Colt CR6920. The bottom portion fits just fine so I can only assume that poor manufacturing is the issue and it was either milled improperly or doesn't fit properly on my rifle as it seems to be ~2mm too long. I attempted to grind the rails back but gave up as getting a proper fit is beyond my ability. Absolute waste of my money, should have done more digging on VISM because it seems they're associated with NCStar and bring with it all of the low quality of their products. Lesson learned, will never buy VISM again.