0-100 PSI gauge guard
1/4 NPT thread (to suit most regulators)
If you are looking here you have probably just damaged or busted your regulator gauge. Luckily they are easy to replace. Just un-screw the gauge and then screw in the new one.
These regulator gauges can also be used on many other devices as the 1/4 NPT thread is fairly standard and it will suit most standard regulators. Annoyingly Micromatic use an unusual Left Hand thread so this gauge will not fit Micromatic regulators but almost all other regulators will be compatible.