I can second NA's answer, my dad has the exact same radio in the first picture, doesn't use anything else, he suggested to me to get this radio as well. and i know from watching my dad that that button is used to slow down the steering. Since i race my car on my 1.5lane road, it's hard for me to turn sharp enough to keep away from those ever-so-naughty kerbs... lost a dogbone from my RS4 3 when i hit one at WOT...also flipped the car too. and my dad is also racing with me and he car turn on a dime. i'm green with envy! oH, and since I need a new throttle servo, might as well replace the electronics all together...