This amazing wireless intercom system utilizes state-of-the-art Bluetooth 4.1 technology to provide a crystal clear link between up to 4 workers, revolutionizing communication, safety, and efficiency. These units outperform the competition in every way. The standard kit includes the ear protection we recommend that fits standard hard hat/helmet mounts. For Protos helmets, select the option without hearing protection. ALL HELMETS SOLD SEPARATELY.