Will fit on aero m4e1 with a little file work. - Strike Industries .223/5.56 Enhanced Ultimate Dust Cover

Great product for the money. Easy on and off and will not beat up your receiver like a metal door will. As for fitting it to the Aero upper receiver, all it takes is a small amount of file work. I did this near the attachment pegs where the body of the door rubs on a couple of raised pads on the receiver. Carefully test fit first, then it's obvious where the door to receiver interference is. Then file, test fit, file untill the door operates without drag. Gave it four stars due to the fitting work described above, otherwise it's a solid five.