Regulator Nipple Right Hand 1/4" MPT
This nipple will link the regulators via their right-hand thread ports.
On most regulators, the secondary pressure has a right-hand thread and the high pressure is left hand.
Some brands have right hand on the high-pressure side so you should wrench it apart to find out before purchasing.
The connector is a right-hand thread meaning you turn it right to tighten an left to loosen.
Hex nipple is a 1/4" x 1/4" MPT connection.