The Bar

Three blondes walked into a bar. The bartender asked the first what she wanted. She replied "I'll have a bl." He thought a moment and then asked her "What's a bl?" She replied, "Well, duh, a bl is a Bud Lite." He turned to the second one and asked what she wanted. She replied "Make mine a ml." He thought ok, if a bl is Bud Lite, then ml could be Michelob or something, and said, "OK, what's a ml?" She replied, "Well, duh, it's a Miller Lite." He then turned to the third one and asked what she wanted. She replied "I'll have a 15." He said, "Ok, bl is Bud Lite, and ml is Miller Lite, but I have never heard of a 15. What is it?" She said, "Well, duh, it's a 7-7."