Unique Button-Hole Mount for the Lavalier Slim Omnidirectional Microphone. The 4160 Series Slim Omnidirectional Microphones comes with a unique Button-Hole Mount. It mounts on the mic head and has a small side-entry pipe (2 mm diameter). The pipe makes it possible for sound to enter the mic when it is concealed in a button hole. The Button-Hole Mount is delivered with the 4160 Series Slim Series Microphones. It should be mounted on the side of the microphone with the silver dot. Sold as a set of five pcs.