This stainless steel pump dispenses directly from a 1 gallon (3.8 L) jar with an 120 mm neck opening. You should measure the outside diameter of your jar opening - including the threads, to determine the proper size. The stainless steel lid will sit over the jar threads. The pump dispenses 1 ounce (30 mL) per stroke with the option to reduce portions in 1/8 ounce (3.7 mL) increments, using the supplied gauging collars. When you place your order, be sure to request a colored knob engraved with your contents for a clean presentation. A white knob is shown, however, black is standard.