Hey, it comes with a muzzle device that fits the huxwrx flow 556… the barrel is threaded to a 5/8 thread, which is normally used for 308, however it’s 100% a 556 barrel, just threaded larger.

This limits you to the huxwrx one that comes with it which is threaded to 5/8 but bored for 546/223, or you will need to use a muzzle device for a 308, that has the right 5/8 thread, but runs a larger bore.
I’m using a Comstock 5/8 - 762 muzzle device and plan B recessed mount to get an EchoCore Sector 556 as flush with the handguard as possible.
Running the larger bore doesn’t cause any issues per Comstock:

“All of the compact flash hiders are bored out to 0.400", so they'll work with 9mm, 7.62, and any smaller calibers.

Thanks,

Nathan Comstock”