Functions as it needs to
The 0.250-inch (stem diameter) prevents the stem from dropping all the way through the barrel, and positions the mirror so that portions of the chamber can be inspected. The mirror is reflective enough to allow me to see my eye when I look directly at it. It does need to be used with a flashlight to illuminate the walls of the chamber. Chamber mirrors are part of the recommended "M-16" complement of armorer's tools.
