It connects to the the purge tank opening. Drain the system as usually, suck all of the air out. The kit has a valve that you then put into a tank of new coolant. The vacuum will draw the new coolant into the system. After you pull nearly all of the air out. I have purchase a non Radkitplus system, for only $100. From the pictures Shadowman has on his website the device appears to be the same. Note that the system has various size rubber adapters that allow it to seal onto the filler necks of most systems.