I was very excited for this product as I had just received the new Print-X SRBS Suppressor and planned to use it on my SIG SG553 Commando. The 553 is the only Swiss SIG with a threaded muzzle . All the others have flash hiders that are integral to the barrel. I was aware that some European manufacturers were making these types of adapters but no one was selling them in the US. I was very happy to see B&T bringing these to the US. Sadly the design only works on my 550. The flash hider on the 550 is significantly longer than those on the 551 (at least the ones I have that were imported by JDI over the past few years). The only way for this to work on the 551 would be for half of this product to be redesigned. I really hope that B&T offers a shorter version at some point in the future so that I can suppress my 551. I have been looking for something like this for a long time.

This is an amazing suppressor adapter for the 55x series. If you have a 55x with a one piece barrel (i.e. integral flash hider), it is worth looking at this adapter. I can personally attest that this adapter works with at least some of the JDI imported 550s and 553 LBs. There is a lot variation in flash hiders on these firearms. The Swiss Army STG 90 flash hider does not have internal threading on the end for a blank firing adapter. B&T Switzerland calls the same flash hider with internal threading the "550 Export", which is what a lot of the imported firearms from JDI have for a flash hider. The "550 Export" flash hider is 22mm in diamter and 54mm from end of the muzzle to where it begins to taper. If you have a flash hider that matches this description, this adapter should work for you. It is my understanding that this adapter can also fit a true STG 90 flash hider if a piece is pressed into it to make up the slight difference in length between the STG 90 and "550 Export" flash hiders.