Jiggers are metal measuring devices that usually have two cones, one on either end. The larger cone typically holds 1 1/2 ounces while the smaller cone holds 3/4 or 1 ounce. The jigger is an essential, aesthetic piece of the bar set up that ensures the precise measuring of liquids. It also facilitates the making of consistent cocktails. Well, at least for those of us with wobbly hands or poor judgment.