1.Compatible Information: Replacement for PMMN4021/21A,PMMN4027/27A,PMMN4039/39A. Compatible with GP Series: GP328, GP338, GP339, GP340, GP360, GP380, GP540, GP580, GP640, GP680 / HT Series: HT750, HT1250, HT1250LS, HT1550, HT1550XLS / PRO Series: PRO5050, PRO5150, PRO5350, PRO5450, PRO5550, PRO5750, PRO7150, PRO7350, PRO7450, PRO7550, PRO7750, PRO9150 / PTX Series: PTX700, PTX700plus, PTX760, PTX760Plus, PTX780 / MTX Series: MTX850, MTX850LS, MTX950, MTX960, MTX8250, MTX8250LS, MTX9250 / PR Series: PR860 and more 2.Premium Material: PMMN4021A Speaker Microphone is made of high impact-resistant plastic housing that is resistant to damage from drops or impacts.TPU coiled cord bring super bending strength, abrasion resistance,scratch resistance and have long operating life 3.Clear Sound Transmission: 3.5mm audio Jack prodive superior quality voice transmission, even if the distance is far, can still provide perfect communication effect.allowing you to clearly receive information from partners.Improve team collaboration efficiency 4.Comfortable to Use: PMMN4021 speaker mic combined with PTT (Push to Talk) button.Styling is ergonomic and easy to hold.The mic clip conveniently clips to your lapel, shirt pocket,easy to pick up,soft and skin-friendly material provides comfort for long-time wear