Not sure - I didn't go look at the links. My AR19B is a 14.7 with suppressor ready pinned flash suppressor that has the Whisper threads for the Whisper suppressor on it. I ordered the Whisper at the same time, and it is awesome!Carbine! Like a 16 inch one? Oh I may have to get one to troll in IDPA and USPSA......finally lol, I have been waiting a while since I wanted an X9 magwell since o don't own enough berreta mags (none in 30 round really) and my Glock mags are for other carbines already.