M-7/DC Amplified Electret (Retrofit Kit) This Retrofit Kit allows you to upgrade your older model headset (H10-40, H10-30 etc..) microphones with our M-7/DC Amplified Electret Microphone which is the latest in microphone technology. Easy to install because you do not have to change the Boom Assembly. Your Price: $106.50 Model Number: 18376G-02 Customers who bought this also bought Protector-Fits M-7A Microphones Comfort Gel, Undercut Ear Seal Filter Filter Protector-Fits all Microphones