Acoustic Tube
You can use the Motorola NTN8371 acoustic tube with headsets:
HMN9727, HMN9752, HMN9754, HMN8433, MDMN4021, MDMN4022, MDMN4028, MDMN4029, ENMN4014, ENMN4017, BDN6664, BDN6726, BDN6668, BDN6730, BDN6667, DN6729, BDN6666, BDN6731, BDN6732, BDN6665, BDN6727, BDN6670, BDN6669