Sentinel LE is a very durable, very comfortable earpiece designed for normal to noisy conditions. This Earpeice is exceptionally durable with Kevlar Reinforced Wire, and stapled strain reliefs. The wiring scheme is what is often referred to as a "Poor Man's Two-Wire", because the second wire leaves the bottom of the PTT molding. The big advantage to this is less wire to deal with than a traditional two-wire. The only disadvantage being that the wires are not long enough to run down your sleeve, the Microphone PTT unit must be worn on the lapel. This is our most popular product because it is practical for almost all applications.