"This is going to be an overall review of the Noveske Gen 4 handguard (ID: 13190) and Gen 4 Noveske Receiver. Other reviews have stated their experience with different of trying to fit the handguard on other non-APS/EMG rifles, but my review will focus on fitment for APS receivers.
By all means this is not a bad part. APS/EMG has made a decent Noveske receiver and rail system. All of the color options come with a matte finish on the receiver and the same goes for the matching m-lok rail system. While it's not my favorite matte finish on a rifle, it's perfectly passable. Overall the finish gets a 3.5/5
As other comments have pointed out in the Q&A section, this kit is only going to be a drop-in for APS gearboxes. However, be aware that even some APS gearboxes will not be 100% drop-in. The only gearboxes that will be a 100% drop-in with this kit are the APS eSilverEdge gearbox (ID: 92813) and the APS eSilverEdge SDU 2.0 gearbox (ID: 16880). Unfortunately, I have the original Silveredge gearbox from APS (ID: 49308) and I found out the hard way that while this gearbox will sit in the receiver just fine, it won't be a direct drop-in and work with this kit. The one part of the gun that won't work if you do not have the eSilverEdge gearbox is the fire selector switch. If you navigate to the eSilverEdge and regular SilverEdge gearboxes and look at the pictures where the selector plate is, you'll notice that the eSilverEdge has a hole below it whereas the regular SilverEdge is flat like a normal Marui-style V2 gearbox. This recess is used to accommodate the gear that mates with the ambidextrous selector gear below the selector plate (This gear is shown on the 5th picture of the eSilverEdge gearbox's store page). Unfortunately, the receiver kit does not come with this pair of gears so you'll need to buy them if you don't already have a gearbox with them (Those can be found here: ID: 87164). If you were to purchase a more traditional Marui-style selector cap (like the one shown here ID: 25898), I'm sure you could get it to function on a Marui gearbox, however, I cannot confirm that this will work and even if you manage to fit those pieces in, you may have to modify other aspects to get the fire selector to work with the regular SilverEdge gearbox and Marui gearbox. My advice: If you plan to buy this, make sure you have an APS gearbox that has the ambidextrous gears and the hole below the selector plate to make sure your gearbox is a direct drop-in.
In terms of usability and convenience features, this kit would be considered outdated because of the lack of these features. Because you'll be buying this kit and do not get the same warnings as if you were to buy the rifle standalone, you need to keep this in mind: NEVER, EVER remove the buffer tube when the gearbox is still in the rifle! Because the wires running to the rear are pressed up against the inside of the receiver and run through the buffer tube, removing the threaded buffer tube will twist those wires and shear them. This is a huge pain in the rear as it prevents you from removing the buffer tube and changing the spring from the rear. Because of this, you'll have to remove the gearbox to change the quick-change spring. Compared to other systems like the QBS for example, you lose a lot of the convenience by having to remove the gearbox. Also, on my kit, I had a tough time knocking out the two receiver pins as they were pretty tight but I assume it will wear down over time and be easier to remove. The one good thing about this receiver is that the magwell is very wide and accommodates a lot of different magazine sizes so you will not have a problem fitting most M4 magazines. Another thing to consider is the grip choice. Grips that have a rear fin that presses against the receiver need to be at a specific angle in order to fit snuggly. This is the original grip for reference (ID: 11404). Choosing an outer barrel is easy with this kit as it will fit most Marui-style outer barrels (I used a ZCI outer barrel and it worked fine). The buffer tube needs to be an APS-style screw on buffer tube (Original here: ID: 87367)
Overall, I like the variety of colors that APS/EMG offers on their receivers, however, this product loses a significant amount of points because of the proprietary nature of its design. The fact that this will only accept a very specific type of APS gearbox is pretty disappointing. Granted, if you were really dedicated and owned a dremel you could get this to fit other gearboxes. However, I simply don't think it's worth the time and money you spend on this product and its components. If you really like the EMG Noveske Gen 4, you're probably better off buying it outright than buying the receiver kit and other parts like grip, buffer tube, outer barrel, and other parts mentioned above. You'll likely spend less money buying it outright than otherwise. If you plan to buy this as a replacement for a Noveske rifle you already own, then it should work perfectly. Definitely would recommend it if you're an APS fan, otherwise, I think there are better options for Noveske-licensed products.