Check the listing for details. Sentex Horizon 3-Wire Intercom Gate Security Microphone -080 Board SN1640010-B. Condition: New. Listed at 9.99 USD. 4042bSB4A.05 New Sentex Horizon H Series (and Possibly Others) Telephone Entry Access Microphones, 3-Wire (Red, White & Black) For -388 Board, Part Number SN1640010-B or SN1640010B. Each bid quantity is for One (1) Microphone. You may bid / buy any number, up to the total quantity available above. These were purchased at an electronics supplier liquidation earlier this year, and they were brand new in the original bulk factory bags. We packaged them in heavy Ziplok bags for resale. These will work "plug and play" with the Sentex Horizon H Series, and they probably work with other Sentex models (may require modifying the wiring harness or changing the modular board connector plug). The systems they are used in are fairly pricey, so they are probably high quality microphones with excellent voice quality. According to our measurements: Overall length, including harness: 18-1/2 Inches Overall microphone module length: 1.258" / 31.97 MM Microphone module length (smaller diameter front portion): .698" / 17.72 MM Microphone body diameter (at front): .500" / 12.68 MM Microphone diameter (at rear): .628" / 15.96 MM Modular plug width: .300" / 7.63 MM Modular plug thickness: .105" / 2.68 MM