It depends entirely on the suppressor. For example, YHM suppressors thread onto a YHM flash hider, designed specifically for their suppressor. Many others attach to most NATO flash hiders, like Gemtech's "HALO". There are some that replace the flash hider altogether, and would be specific to the threads on the barrel of the rifle for which they are designed like Surefire's.
Does this help?
Does this help?