This is a dust plug that is also a secondary pressure seal. It is removed only when a test is to be run. GTP-235-9K is the standard plug for the GTP-235-3/8 coupler. GTP-235-9SK is the standard plug for the “AH” and “S” couplers. The standard plug is included unless otherwise specified. If the tee handle plug is desired, the customer must specify (GTP-235-9T for standard length, or GTP-235-9ST for “AH” and “S” couplers).