I happen to sell them there are a few diffrent companies most common is the asco setup you can get them in 1/2 or 3/8 I happen to have a slightly used one it is either front back or side to side 125$ but you can expect to pay around 300$ for a 8 function in a 3/8 but the ease of use and not having to buy the extra fittings works great plus they usually have 1/8 gauge ports built in.
I have a set of dual EAI Blue valve's never used them and there are just sitting in my tool back. They are 1/2 not to sure about them a buddy gave them to me, he was putting them on all the vehicles that he was doing.