Primo EM283 Figure of Eight (bi-directional) electret capsule - micbooster.com
5 x OMNI DIRECTIONAL ELECTRET MIC CONDENSER MICROPHONE CAPSULE 6mm DIAMETER | eBay
Electret Condenser Microphone Units 9.7*4.5mm High S/n More Then 60db Used For Consumer Electronics Capsule Microphone With Pins - Buy Electret Condenser Capsule Microphone Units 9.7*4.5mm With Pins,More Then 60db Used For
10 Pcs/Lot With 2 Pin Cables Capsule Electret Condenser Microphone 9767 Mic for Phone MP3 Laptop Digital Camera|Microphone Accessories| - AliExpress
A potentially novel pre-amp for electret mic capsules which have their internal FET's Drain and Source connections available separately