The ARC T21 Series One-Wire Surveillance Microphone is a high-end, professional earpiece used by many enterprise B2B, government, security and hospitality customers. The T21 is easy to conceal and the miniature earpiece leaves your hands free. The Knowles microphone delivers superior voice communication. The Kevlar reinforced cable gives you durable strain relief and the microphone is attached with a 360-degree rotational clip. The acoustic tube is replaceable and the T21 comes with an open ear insert for situational awareness. Compatible with the following: Motorola GP1280, GP140, GP320, GP328, GP329, GP338, GP339, GP340, GP360, GP380, GP640, GP650, GP680, HT750, HT1250, HT1250LS, HT1550, HT1550XLS, MTP700, MTX8250, MTX8250LS, MTX850, MTX850LS, MTX9250, MTX950, MTX4500/4550, PR860, PRO5150, PRO5350, PRO5450, PRO5550, PRO5750, PRO7150, PRO7350, PRO7450, PRO7550, PRO7750, PRO9150, PTX700, PTX760, PTX780