I ran a 575M6 for 12 years on many radios , was my mic of choice , always thought the D-104 hand held was to damned loud and that the 575 sounded better on sideband ....OK ...i've always wondered about the RD-104s ? ...one of the only mic's I never had the pleasure of using ,Don't even think I ever heard one ? I know longer use my 575M6 , I really dont know what in the hell I was thinking all of those years ? I personally do not like road noise or back ground noise coming in when IM modulating , but I also like NPC and Swing Kit mods on my radios which basically takes audio off the scale ...my bad ! ....after all these years I kind of did a servey on how drivers were sounding out there on the open roads and I narrowed it down to whom really sounded the best out there (more like the base station on wheels effect if you will) ...well 9 times out of 10 it had all came down to the same damned mic out there ....Yeap !! The Turner/Telex Road King -56 ....IM totally impressed to say the least !! and most of the ones that did sound like base stations on wheels were followed with a very nice touch of echo on the side ....REMARKABLE !!!! .....after all these years ...thats what this dude wanted to sound like !! No wind trunnel ,No road noise ,No over modualtion , .......I mean the windows rolled down and the stereo on in the back ground and this RK-56 just likes what the lip gaurd will let into it !!! .........yeah IM sure it has to do with how that certain radio is tuned and what not ....but IM sold on this non-powered NC mic !!! been going strong with mine for over 2 years now ......I still here them ask me every now and then If IM a base station !!!! Man !! You talk about CB EGO here dudes !!! (-: ......but I suppose the bottom line here is that we all have different type voices out there .....different radios and different tunings on those same radios ......so what might work for me ,may not work for somebody else .....there has been a lot of good mic's come my way over the years (and I always thought I needed a powered mic to be heard ) ....I was wrong ....the radio just needed to be tuned how I like it and how I like to be heard .....IM even hearing stock mic's these days sounding loud and proud and clean as can be (radio tuning) ........still would like to try a RD-104 one of these days for grinnies .....but I doubt anything will come close to the performance of my Road King 56 .....oh and by the way .....they have a copy of the RD-56 .......I think it's called CDL-56 ......FORGET IT !!! ...it just dont have the drive and or push of the Road King ....in other words ....you get what you pay for this time around.