Because i was nervous about how thin the remaining steel was going to be at the juncture between the primer socket and the tool slot, (see photo) when the primer socket was enlarged to use the PRbullet adapters. The tool slot is only needed to be used once, to marry the plug to the barrel, then it is never used again. However, this plug didn't fit the barrel so very good, so i could have used the tool slot once more. Instead had to use a pipe wrench, after using Busta' suggestion to use the chamfer on the end of a 5/8" bolt to open up the rim on the end of the plug.