5KU (Airsoft Surgeon) CNC Aluminium Magwell - STI - Blue
Don't be put off with the brand, this is one product they can do right!
I personally use one of these and they're perfect, they’re exactly the same as the Airsoft Surgeon ones.
Once attached allows for faster reloads and aesthetic improvements.
* All magwells come with the retaining pin.
* Colour may differ to picture below