Pro''s: I bought 2 of these rifles, and they are fantastic. The replicate the size and feel of the real thing, in almost every way. They already have the Magpul upgrades, which saves you from having to buy them seperately, then have the originals sitting in a box somewhere. The magazines are easy to load. The rifle fires well, and very accurately, even after running 1000 rounds through it without cleaning. You can practice marksmanship and combat drills all day for the cost of a couple magazines worth of 5.56mm. The buffer tube is mil-spec dimensions, for those who are wondering. The trigger mechanism is a standard AR-15 size, so you could easily replace it. It has a quick disconnect sling swivel, that can be attached to a metal attachment point on either side of the buffer tube. The selector switch rotates 90-degrees to the typical "semi" position for firing, unlike the Umarex/Colt that rotates 180-degrees. The barrel is solid, unlike the Umarex/Colt that has a decorative "sleeve" over a thin inner barrel. The flash suppressor is threaded on the muzzle with standard 1/2"-28TPI threads, and could accept a sound suppressor. The bolt can be completely removed out the back, just like a real M4 [and unlike the Umarex/Colt]. Con''s: The rifle has a couple disadvantages, although it''s still a great gun. The whole thing is polymer, except the bolt and barrel. That makes it about 1lb lighter than a real M4 empty, and over 2lb lighter when loaded. The buffer tube is polymer, and is molded directly to the lower receiver, so don''t do any drills that would require you to fall/land on the rifle (3-to-5-second rushes). The selector switch ("safety") is polymer too - it''s held up well so far, but I could envision it breaking. Since the .22LR rounds single-stack in the magazine, it only holds 25, which could lead to an unnatural expectation of when M4 mags will run empty. Since the buffer tube is molded to the receiver, you can''t add aftermarket sling swivel plates into it. There is no dust cover, so be careful of drills where you roll around on the ground. There is no bolt forward assist, which can cause issues with malfunction clearing drills (S.P.O.R.T.S.). Other: There is a hole in the buffer tube, if you remove the stock, so you could add weight in there.