The Inner ear. I actually only attach this ear with the lower hole and the hole where the stalk goes through. If youll be running a servo for your stalk, I suggest adding another hole and screw on the upper part of the ear. Take the inner ear and drill through the urethane. On the back of the ear, use a countersink bit and add them to the holes so the 4-40 head can sit flush. Now, place the screws inside the ear and attach the nuts. The nuts will align with the outer ear cap and the out ear cap will press right in. . Next drill out the holes on the helmet body for the mounting screws (long 4-40 screws). Once that’s drilled, place the inner ear on helmet and attach the screws on the bottom. Take your RF stalk and place it on the inner ear and attach it with the screw, nut and washers provided. After this the ear cap should pop right on, if the nuts are lined up correctly.