For HMT-1 and HMT-1Z1. Intrinsically safe (IS certified) when used with the HMT-1Z1.The Ear Bud Hearing Protection Headphones play audio from the HMT-1 and HMT-1Z1, and provides hearing protection from high noise environments. They have replaceable foam tips made of premium memory foam, and are 33dB NRR (Noise Reduction Rated). They also provide privacy for any audio coming from the HMT-1 and HMT-1Z1, and provide an optimal experience when using remote video applications. The headphones are designed with a custom cable length and right angle connector optimized for use with the HMT-1 and HMT-1Z1. Each headphone comes with a pair of Medium foam tips; other sizes are available separately.