A Type 1 valve is attached to a hose from your grill with a large plastic screw connection that must be completely tightened to engage the valve and operate properly. A type 1 valve also has an internal threaded fitting that allows the use of a POL connection in addition to the external plastic threaded fitting. A Type 2 connection is a spring-loaded connection; a metal ring on the tank slides back to engage the hose and snaps back into place to ensure a tight connection.