Thank you for your quick reply, unfortunately I've purchased this M4 used a couple of years ago and don't know what brand it is. I do however have picture which will show the two receivers and the two pieces of the hop up system.
Sorry I couldn't attach the pictures directly to the post, let me know if the google drive link doesn't work.
https://drive.google.com/folderview?...fJQCGP8XPrQIG8