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Fairly new from HERA Arms — imported and sold in the U.S. by LAN World — is the SFU, or Side Folding Unit. This stock adapter allows for folding the buttstock to the side and fits any rifle that accepts an AR-15 receiver extension (buffer tube). However, it probably won’t work on your AR-15. . .

The SFU is one sleek, slim, lightweight folding adapter. There are certainly a lot of clunky ones on the market, and this ain’t one of ’em. It looks like this on the top:


…this on the bottom, with a good view of how thick that steel hinge pin is:


…and this on the push-button release side:


As you can see, the SFU is the same diameter as a castle nut, providing a sleek, in-line appearance.


I’ve actually installed mine upside down so the stock folds to the right side, but it’s really designed specifically for folding to the left. When installed correctly, a castle nut isn’t even needed. A set screw inserts in the threaded hole on bottom, indexing with the 6:00 slot in the buffer tube’s receiver threads and ensuring that your stock is perfectly timed vertically with the SFU.

However, obviously it works in alternate orientations and, really, you could lock it to your receiver so it folds in any direction desired. Installation consists of screwing the SFU’s male side into the receiver until the unit is aligned properly…


…then tightening down the two hex bolts, which clamp the SFU’s body solidly to the receiver.


Pretty ingenious, really. It’s as simple as it is solid, while allowing infinite adjustment.

At this point, it’s probably obvious why the SFU won’t work on most AR-15s; it caps off the receiver and blocks the buffer tube. So, HERA’s Side Folding Unit is relegated to rifles and shotguns that accept an AR buffer tube — either from the factory or via an adapter — but lack your standard AR recoil system (bolt carrier passing out the back of the receiver and into the buffer tube). The CZ Scorpion Evo (SBR) here is a perfect example, and there are plenty of AR buttstock adapters for AK-47s, shotguns, and other firearms in addition to AR uppers that don’t require a receiver extension. Still, it’s a niche product for sure.

Lockup is achieved through a claw that’s depressed by the release button.


It very smoothly and easily snaps over a stainless steel pin on the receiver side, holding it firmly in place with no wiggle. Although the pin is solid and both it and the claw are steel, I’m guessing one of these things would be the weak point under extreme stress. Of course, I suppose this would be preferable to a cracked receiver.


Despite the ease with which it clicks into place and releases, the lockup is rock solid. When folded, there’s very little wiggle in the hinge either, but it glides with ball bearing smoothness.

Speaking of ball bearings, there are a couple of those inside the hinge area that act as detents when the stock is folded, although they’re pretty gentle in that role. They aren’t likely to keep most AR stocks folded if held side-down, but they’ll keep it in place while shooting with the stock folded.


On a rifle that doesn’t shoot reciprocating parts into the buffer tube, HERA Arms’ Side Folding Unit is lighter, sleeker, and less expensive than most alternatives and it’s a solid, well-made piece. Fit, finish, and function are aces. I dig it.

Specifications: HERA Arms SFU

Price: $115.00

Ratings (out of five stars):

Fit & Finish * * * * *
Machining, fit, and finish are basically flawless. I thought the install was pretty straightforward despite the German-language instructions, but LAN World put together a pretty good YouTube tutorial anyway.

Function * * * * *
My Scorp may be caught in 922(r) limbo, but I’ve been using this SFU for a few months in my dreams and it works great.

Overall * * * * *
I realize I’ve already described the SFU as a good deal, which it is compared to some of the larger, clunkier competition, but $115 still seems a tad steep. Then again, for whatever it’s worth it’s made in Germany rather than somewhere in SE Asia. You can’t beat it for sleek form factor and smooth but solid action.

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    • For sure. It actually seems kinda rare to find a chassis system that accepts an AR stock and doesn’t already have side folding built into it (?), but chassis rifles are definitely a solid target for the SFU…

  1. Here’s what I don’t get: Everybody that makes a side-folding stock, makes it so that the stock folds to the right and covers the ejection port, making the rifle unusable until the stock is folded back out.

    On an AR, it doesn’t matter as much because, unless you’re using a bufferless setup, you can’t use the rifle until it’s folded out, anyway. But on AKs, shotguns, and just about every other semiauto rifle that isn’t a traditional AR design, it doesn’t make sense.

    • I installed it upside down on purpose (which is mentioned in the review). I wanted it to fold to the right, but the SFU is specifically designed to fold to the left. However, it can be installed to fold in any direction you want, as it’s infinitely adjustable 360* around.

      FYI — many fold right but don’t block the ejection port because the stock is designed to leave that area open. The U.S. generally seems to prefer stocks that fold to the right. For me, I installed it this way because if I’m carrying the gun on a sling I want the flat side against my body rather than the folded stock against my body. But I may swap it up so it can be fired folded w/out the stock blocking some of the ejection port.

    • Oh yeah, there’s no shortage of folding adapters out there. They’re just all big and clunky and/or more expensive in comparison. The SFU is the sleekest, cleanest one I’ve seen and it’s smooth as butter and locks up solid, so I’m definitely digging it.

      • There is a US company that sales almost the exact same part, has two allen screws on the 1/2 that attaches to the stock that the HERA does not have them. I had to look to make sure the one I have was not a HERA unit, cause I know I have not ordered from their US distributor. HERA also makes a HK SL8 stock adapter. I have non HERA one sitting here I was going to put on my new HS3 but it seems that a Savage 12 F/TR won’t work in that stock. Now have the MDT HS3 for a SA Savage with their Skeleton Rifle Stock but no action for it. Trying to figure out what to put in it.

        • Hey Ed, turns out it’s a white-labeled version of HERA’s part. So it’s made by HERA then the logo of the other company is slapped on (with permission). The design difference was due to it being an older version. The one reviewed here is the new version, and I do believe the only place to find it is LAN World, HERA’s U.S. importer/distributor…

      • Sent an email to the site’s email address with a link to the other company site. And an offer to take pics of the one I have sitting here.

  2. Here’s one thing to mention about these side folding units that I haven’t seen mentioned. They weigh close to a pound. For something like a CZ Scorpion or a short barrelled PDW it isn’t such a big deal, and the added weight is worth the ability to fold the stock. For others, it might be a concern. I wanted one for a custom MKA 1919 and adding a whole pound to a gun that is pushing closer and closer to 10 pounds loaded just didn’t seem worth it. I bought an MDT side folder and would not recommend it to anyone for anything. It has no way to tighten the hinge, and it swings looser than a couple on qualudes at a 70’s key party. I consider that useless. I think the average buyer would pay an extra thirty dollars to have a pair of detents and recesses machined into the hinge so that the stock locks in the open position.

  3. I definitely don’t want to pay for the stamp to go sbr I just want a swivel arm brace do you think that it would work for just that ?? And do you recommend KAK or a Sig arm brace ??? On my cz scorpion !

    • Nice to hear from another Vector owner out there. The safety switches don’t interfere at all, then? I’m THIS close to throwing a Hera SFU into a basket and pulling the trigger, but that clearance issue is the only thing that has been stopping me, as I have the Gen 2.1 version…

  4. This appears to be the same thing as the XLR folding adapter. I can’t find any differences in appearance between the two. However this one seems to have bearings to somewhat lick it in the folded position.

    The XLR is easy to buy. But I can’t find anyone who sells this SFU one.

  5. The SFU originally on the XLR website was the HERA unit. XLR simply had HERA modify the design for them to include two set screws to adjust lock-up and eliminate any play that may develop with wear for the units they sold under the XLR branding. It appears that XLR recently began selling a different version of the SFU manufactured by someone other than HERA. I can tell you the HERA SFU is top notch and only improved by the addition of the adjustment screws as specified by XLR. One difference is the LOP is shorter on the current XLR version compared to the HERA, if that matters to you. I do not have experience with the new XLR SFU but trust that those guys found a different winning design to offer for their chassis customers. The people at XLR are very knowledgeable and helpful. The HERA unit is also available at Ranier Arms.

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