The Female ground joint has a grind on the inside of the glass and acts as the outside piece. The Male ground joint has a grind on the outside of the glass and acts as the inside piece. The first number in the name is the width, in millimeters, at the top of the ground joint. For example, 14/23 means that it has a width of 14mm at the top and will match with other 14/xx ground joints. The second number is the length of the grind. For example, 14/23 means that the entire grind on the ground joint is 23mm long. This will not change compatibility as long as the first numbers match up. Please feel free to call us if you have any further questions.