Not a bad accessory at all, if you're looking for a full milsim look, then this is what you want.
The suppressor is strictly for looks, it doesn't make the marker silent. I've been asked by both my friends and other players if it's real and where do they get one, so if anything, you gain some respect on the field from other players.
The strengths of the part are that the set screws are actually plastic, so it doesn't scratch the barrel at all, and that it's very durable. Also, it looks wicked if you have an assault rifle or sniper setup.
There are a little more weaknesses on it than I would have though. One is that it doesn't silence the marker, if anything, it makes it louder because it will usually cover the portholes on the barrel, which was the case with my BT-4. On longer barrels, it throws the balance off a little. And finally, other than looks, there's no real function.
I'll give this an 8, it's a great accessory to have if you love milsim, but it's not really that functional.