Most custom-made hearing aids have a vent hole which runs through the hearing aid, from canal tip to faceplate.  The vent hole can easily become plugged with earwax, so you can use the vent hole cleaner to poke out any debris that has collected inside the vent.  This tool should not be used inside your receiver hole (which is located on the canal tip) nor should it be used in the microphone hole (which is located on your faceplate).  Take care when using this product so you don't insert it into the wrong hole!