EZ-Fit clear voice tube, compatible with Plantronics H51 headset 1, Headset Clear Voice Tube. 2, Compatible with Plantronics H51 headset. 3, Easy To Install Design Quickly Replaces Worn-Out Or Dirty Head Tubes for Convenient Use. 4, You should replace this vital part of your headset if the tip becomes clogged or damaged in any way. For best performance, routinely replace the voice tube every six months. 5, Packaged quantity: 1PCS Clear Voice Tube.