The Tokyo Marui M4A1 System (comes exactly as shown below)
This is a great weapon. Although being kind of pricey on most websites, this is worth it. I purchased mine about 3 months ago, and the modding possibilities are endless. It comes with three rails and screws for each to attach to the forearm, and the upper rail runs the entire length of the upper receiver. Most of the cons weren't that big of a deal, but annoying at the least.
As for the internals, they are Tokyo Marui, and the EG1000 is impressive in my eyes. Much, MUCH better than any other Echo 1 or Jing Gong. If you opened up the gearbox of a TM and set it next to an Echo 1 gearbox, the quality difference is immense.
As for the externals..
Pros6 position buffer tube compatible with real-steel collapsible stocks
Upper rail Runs entire length of upper reciever
Forearm rails included
Several metal parts
Flip-up front and rear sites included
The plastic parts feel high quality
ConsBuffer tube and buffer screw are 1 piece (I wasted money on a buffer plate and wrench before I found this out, damnit.)
Doesn't come with a foward sling swivel/adapter
Both lower and upper receivers are plastic (all TM M4/M16 series are like this)
Pistol grip is already loose (probably just my gun)
Thanks for ready, please tell me if this was helpful.
- BTW I got mine at airsoftshop.com