Fast Cap Adapter Compatible with BYRNA SD EP LE - Boost Cartridge Quick Change with Hex (Black)

I bought the Fast Cap Adapter for my Byrna SDXL launcher and I am very happy with it. It makes changing the CO2 cartridge so much easier and faster than using the factory cap and the magazine tool. I can just twist the cap by hand and replace the cartridge in seconds. No more fumbling with the tool or worrying about losing it. The Fast Cap Adapter is also compatible with the Byrna Boost Adaptor (XL), which allows me to use 12 gram CO2 cartridges instead of 8 gram ones. This gives me more shots per cartridge and more convenience, as 12 gram CO2 cartridges are widely available everywhere. The Fast Cap Adapter is made of stainless steel and has a polished finish. It looks great and feels sturdy. It fits snugly on the CO2 chamber and does not leak or rattle. It is easy to install and remove, and does not damage the launcher or the cartridge. I highly recommend the Fast Cap Adapter to anyone who owns a Byrna SD, EP or HD launcher. It is a great accessory that improves the performance and usability of the launcher. It is worth every penny and I am very satisfied with it.

Works great, fast and easy to unscrew and replace CO2 cartridge. My Kydex IWB holster needed a slight mod for the extended length but that was fairly easy.

11/26/2025 - I see differing reports on how these look in the reviews so I'll confirm that as of this date they are the matte black finish, brand text on the side edge (not front as pictured), and threaded correctly for proper fit. Looks and fits perfect in my opinion and the build quality is good. Easy to screw on an replace and the price is right. I think the grip texture on these is better than what I'm seeing from some of the other options too.

These work on an SD

That's all this is and all it needs to be. The Byrna will let you empty a few mags on one CO2 cylinder, so maybe it's not important to be able to quick-change the cylinder like it could be to load a new mag. Still, having to find an Allen wrench when you do need to put in a new cylinder is a pain. Put this in its place and screw and unscrew using your fingers. The Byrna really ought to come with this piece.

Works great, but I am a little disappointed that K20 decided to put the K20 Tools on the side of the cap, and not on the front - I actually liked that.

Well, I was trying to post a photo of how it fits me Byrna LE model, but Amazon policies don't like that. So, does it fit? Yep. Easy to screw on/off using your fingers? Yep. No need to use that wrench part on the mag. Not sure why Byrna didn't make a thumb screw cap, but at least somebody did.

I love the idea of having the ability to change a co2 cartridge on a Byrna without a allen wrench (even though there is a built in allen wrench on Byrna magazines). II bought 2 of these and same results on both on 2 different Byrna SDs. The cap will screw in without binding - without a co2 cartridge. But with a co2 cartridge the cap binds within one thread screwed in. I did not force it because I didn't want to cross thread these caps or my brand new BYRNA SD. And trying several different brands of co2 cartridges - the same results on all. Maybe these caps were designed for the larger Byrna that holds a 12 gram co2 cartridge, but this product is advertised as fitting the SD. And a message for this supplier: I am planning on buying several more Byrna's to give away as gifts. So far I have bought 3, 2 are gifts to family. I would have bought one of these caps for each of the gifted Byrna's.

Easier than using the mag key . Thank you !

Très pratique

Unfortunately the wrong finish was sent to me. The listing has the finish as matte black, however the item sent was unfinished aluminum. Disappointing, as this does not match the rest of the Byrna. That said, it does fit.