MECoral Dosing Caps are designed specifically for the MECoral Gallon jugs. The fitting accepts standard 1/4 inch RO rigid tubing. The same size used by most dosing pumps. Cut a piece to fit inside the container so it picks up from the bottom, and run the other end to the dosing pump. These caps make changing out jugs very simple. 2 caps are included per order. Do not tighten caps down all the way as air needs to enter the container.