Solid upper - Aero Precision M4E1 Threaded 10.5in 5.56 Complete Upper Receiver with Flash Hider

I like this upper for slow, low-volume shooting. It's very light and maneuverable. I think this is great for beginners, kids, and women who might struggle with the weight of a beefier upper.
The handguard is very slim and gets hot quickly, especially if you plan to use a suppressor. I also think Aero is getting kind of expensive for the quality. Considering BCM uppers come with a BCG, I think they are a better value for someone who will be shooting a lot.