CGA 520 Inlet Nut and Nipple with Filter. Nipple for Uniweld regulators only. This nut and nipple is for the New Style Uniweld regulators.
The New Style has the seat assemble (parts #4 and 5) that is accessed through the rear of the regulator through the nipple as pictured in the breakdown.
Regulator pictured in breakdown is a R-B and is for reference only.