I have a 80s era SPH-4 helmet that was modified for use with the cut-away face plate type AN/PVS-5 NVGs. The surgical tubing that wrapped around the helmet is toast so that will need to be replaced at some point. I decided to show a rather uncommon (in the Army at least) oxygen mask setup, mounting a MBU-5/P Quick-Don mask with the SPH-4. This was in fact done in the Army by some fixed wing aviators and also available for rotary wing use if a O2 system was installed. It is shown in the 1984 dated Army FM 1-302 with a SPH-4, but the QD MBU-5s were more commonly used in the USAF with the H-157 type headsets. When headset worn, a special head harness that mounted to the headset was used that had the snaps for the mask to attach to. The SPH-4 series helmets had O2 mask snaps mounted above the chin straps on the ear cup retention assembly. A special wiring harness is on the quick-don assembly which is a unique feature of the setup. When the setup is worn, the boom mics wire is unplugged from the headset jack on the rear of the helmet or headset. The cord on the mask has a Y split with a mic plug and a mic jack, the mic plug is plugged into the helmet or headsets headset jack and then the boom mics cord is plugged into that jack on the masks cord. This allows both mics to be plugged in but the way the system on the mask is wired up allows only one mic to be hot. When the mask is in the donned position, the mask mic is hot and the boom cold, then when they mask is released by pulling the black knob this disconnects the mask mic and makes the boom mic hot again. The mask when not worn will hang at your chest.