The 20mm Mix & Match eyes have a slightly smaller Iris so they will fit in nicely in our 18" Mix & Match kits and you will see some white around the eyes. Of course they can be used in other kits too if you like to see more white of the eye. So only difference compared to normal 20mm eyes, is size of the iris. ( -1 to -2mm) You can select Full Round or Half Plate on the product page.