Because the first version had been an option in Discovery 2's id just assumed it would have been in the D3/D4's too as well just like our L320, but then I was trying to look up ARC (Active Roll Control) parts for D3/D4 to see if they were same as RRS but couldnt find them listed, thought i wasnt looking in the right places, but kept googling to find out they dont have it, WOW very suprised, along with RRS only having the TDV8 option it really was spoilt.