The optional Yapalong 4000 open mic "Boom Mic" headset. Dual-pin audio plug - 3.5 and 2.5 mm stereo (two prongs). A college field hockey umpire said, "I tried both headsets and prefer the airtube piece over [this one] because it fits my ear better. It is less cumbersome, stays in the ear better, and more comfortable. The only con is that you do lose a little bit of sound level, but you can turn the volume up on the radios so it's not a big deal."  SHIPPING: 4-6 business days, via UPS Ground