Choke tube markings are a series of lines, notches, letters, or numbers that help identify the size of a choke tube. The letters EF are usually written on the outside walls of the choke tube, and it can be confusing if you haven’t seen it before.
EF stands for EXTRA FULL. It designates the choke tube constriction size and in this case EF is between a Full and Turkey choke with regards to tightness. It measures 0.682” in diameter for standard 12 gauges.
Extra Full chokes are used for turkey hunting and they help provide tight patterns at distances of over 40 yards. If you see “EF” written on a choke tube, you can be sure it’s tighter than a Full choke.
