As a general rule of thumb, make a fist with your hand,Bend your arm so your fist is straight up and down in front of your face,and then trace your arm on a piece of paper from your elbow up around on both sides.That will give you a general size of a turkeys head and neck at life size. As for the Browning Invector plus, Cabelas, Bass Pro and Midwest Turkey Call Supply all carry chokes for that gun choke style.