This gearbox is awesome. I had to get a new gearbox when the little nub that holds in the trigger assembly broke on the stock echo 1 box, the echo box is nicer then jg's but it doesn't compare to this one in any way. Systema makes really good quality stuff, this isn't just reinforced in the back like other reinforced gearboxes, this thing is built like a tank! The only drawback is pretty much the price (but hey, it's a Systema) and it's only the box and selector plus 7mm bushings. Overall I don't regret it at all.
Engraved Systema on the side adds a nice touch
7mm bushing will hold up better then 6mm
reinforced all the way through, not one place is forgotten
Gears don't touch the box and run smoothly
REALLY easy to shim
Made of high quality steel
Bushing are kind of hard to put in place but it could be a pro
only the box, selector plate, and bushings
It is really hard to come up with cons for this!!!