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.

This newer version by K20 Tools is GREAT compared to the earlier version. Easy to remove after CO2 cylinder expended - no tool required - looks GREAT!

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.

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.

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.

The image shown to me from this listing was for a matte black cap, but I received a shiny silvery one. Not an issue, but I'd have rather liked it in black. It does thread all the way into my Byrna SD without CO2 (8g) installed, but only two threads deep with CO2. After a quick shake test, I was pleased to learn that although threads are still visible on the cap after installing, the CO2 is snug in its spot as it should be. I'm receiving the CO2 booster soon and I'll update the review if anything is different with that. EDIT: I'm an idiot and tried to install the CO2 Booster on top of a SD with HI VIZ installed (off market?) Instead, I fit-tested for the boosted on the LE and it sits very nicely, leaving less than half a thread exposed with the 12g CO2 cartridge installed

Before you buy this cap, fyi,it's not worth 10 cents. The only reason I gave it 1 star is bcuz it wouldn't let me post this until I gave it a star! Doesn't seal, and when I barely tightened it,it stripped where the allen wrench goes in! I barely turned it and it stripped.

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.