||My TM AUG hopup unit worked great for the time that I had it. Over time it kinda got worn out and the adjustment wheel broke one day.
I looked units for the AUG and found this was the only one available  Note of caution, the Classic army and G&G aug hopup units are different from this one. They take a V7 hopup hybrid unit for the m14. This will only fit in Maruis and the JG ones. Not CA and G&G ones.
Anyway… On to the pros and cons 
• Comes with all the extra screws. If you lose the original ones its no problem.
• Full metal means airtight. If installed properly you will not lose any bbs when reloading. Very tactical ;)
• Good brand (G&P is one of the best on the market)
• Boosts FPS (about 10-16fps on average for me before and after)
• Not TOO expensive.
• Made my 30rps field/CQB rifle into a scary long range DMR.
• G&P’s only shortcoming is their hopup buckings and nubs. They aren’t the best. Look it up on ArniesAirsoft forums. It’s a pretty common complaint. I kept my TM stock bucking in the unit. I have a Angel custom metal H-nub coming in the mail.
• Price for some people. Its $35, but its worth it.
• The Marui unit has a sticker next to the adjustment wheel telling which way to turn for hopup. This unit doesn’t have it, but that’s just a preference. A pet peeve of mine
Besides the iffy bucking and nub performance this thing is amazing. I recommend a Prometheus Purple, TM stock, Guarder Clear or Madbull shark bucking. As for the nubs, the SCS concave ones, along with the angel custom H-nubs and madbull fishbone ones would work great in this.