I am posting this for all the Sig SR9 owners out there. The Sig Sauer SRD9 has been one of my favorite suppressors and I have been 100% happy with the purchase... but one thing has always driven me nuts - no tri-lug adapter. Yes, the Sig SRD9 comes with one of the best out of the box kits in the industry with both 1/2-28 and 13.1x1LH pistol booster mounts and a fixed lockout all included.
This allows owners to be able to use these mounts for both modern pistols and direct thread PCC carbines and even 300BO subsonic rounds. Since the SRD9 is completely user serviceable, owners can also use it for smaller caliber rounds like .22LR, .22WMR and 5.7x28. It is a fantastically adaptable suppressor with suppression that matches my Liberty Mystic X, but with a length several inches shorter. With all the awesomeness of the SRD9, not being able to do tri-lug mounting is a major downside. Tri-lug mounting is fast and secure for all but 99.999% of fixed mount PCC and rimfire applications. The tri-lug is a well proven and secure mount for all pistol calibers on fixed barrels, but we still need the boosters for Browning tilt type pistol barrels.
Tri-lug mounts are the fastest mounts on the planet - just a pull down and 1/3 twist is all that is required to securely mount and remove suppressor for any PCC style firearm all in a very compact and durable mount. With that said, the SRD9 is freaking an incompatible island unto itself with an oddball 1.125-24 thread that marries to nothing. I measured threads and thought I had it figured out with a KAK 1.125x28 tri-lug adapter, but the thread size was wrong. Just before sending off the adapter I designed in Fusion 360 to my machinist, I found Ecco Machine’s adapter. Praise the Lord! I found a stainless magic unicorn adapter for 1.125-24 male to 1.125x28 female all for under $70 at Ecco Machine. My credit card could not get entered fast enough. The Ecco SRD9 adapter screws in and then the $70 KAK Tri-lug adapter (notably one of the more affordable) screws in and you have a high quality all stainless tri-lug mount for your SRD9. Getting a complete all nitrided and stainless tri-lug adapter for any suppressor for $140 is a decent deal, but for this SRD9 unicorn it's a steal.
https://www.eccomachine.net/product/sig-srd-9-45-alpha-adapter/
https://www.joeboboutfitters.com/Kaw-Valley-Precision-MACH-Modular-Linear-Comp-9MM-p/kvp-mach-3lug-mt.htm