1.Vertex Standard EVX-531,VX-241 two way radio professional surveillance earpiece headset is optimized for communications intensive environments in which personnel need to interact with customers while maintaining radio communications. 2.3.5mm 1-pin 4 Pole, 1 spare earbud included. 3.Suit for EVX-531,VX-241,vx-231,Vx-351,vx-261 etc. 4.High quality transparent acoustic tube headset that could hardly be detected by people around you(also reduces electronic radiation), ideal for surveillance purposes and security at airports, casinos, crowd control, conventions, concerts and other working environment requiring discreet communications. 5.Excellent for use in police, military, nightclubs, bars, paintball, security, restaurants, hotels, bouncer, warehouses, and noisy environments.