The Koss SB45 (as opposed to the SB40) DOES contain an electret mic insert. I find this headset very good as an alternative to the Yamaha CM500 which, for some inexplicable reason, is unobtainable in Eu. 73 Tom G3OLB GM4LMH wrote: <The Koss SB40 is fine with the K3 if you remove the nasty dynamic insert and replace with an eletret insert.>