all the ones im seeing on summit have an inlet and outlet. im guessing the inlet is just the hose from the radiator like on stock catch cans, but whats with the outlet? is that just where you hook up a drain valve?

 

I bought the JAZ recirculating can and I'm gonna say the Bottom fitting goes to the radiator and the top is merely for ventilation/filling. Serves the same as a factory overflow tank does. Factory can has the hose on bottom and a vented cap.

Some of the others have the petcock on bottom for draining. Those are used just as catch cans which are needed to pass tech inspection while drag racing. You make a pass, drain the can, make a pass, drain the can. if it's catching any anyways. A drag racer usually isn't worried about recirculating coolant like a street driven vehicle.