Will not work on m4 - Carlson's Choke Tubes Benelli M4 7- Shot Magazine Extension

This tube is about 3/4” too long, which will not allow you to tighten up the barrel enough to seat it. I’m going to try to find a spacer to fill the void until the correct tube becomes available elsewhere. The nut will extend past the barrel in this current configuration. That’s about $70 down the tube, no pun intended. Btw, what color is this thing supposed to be?