A mixing device (10) containing a housing (20) that defines a mixing chamber (30), an A-component feed channel entrance opening (40), a B-component feed channel entrance opening (50), and air feed channel entrance opening (60), and an exit opening (70) where the feed channel entrance openings and exit opening provide fluid communication into and/or out of the mixing chamber, and a static mixing element (80) housed within the mixing chamber between the three entrance feed channels and the exit opening, wherein the air feed channel entrance opening having a cross sectional area that is 0.7 square mm or greater and 7.7 square mm or less.