Compatibility summary
Your Philippines plug may fit in Montserrat outlets, as both use at least one common plug type.
Plug comparison
Philippines plug types: A B C
Montserrat plug types: A B G
Both countries share at least one plug type (A B C and A B G), so some plugs may work without an adapter. Check your appliance.
Voltage comparison
Philippines: 220V, 60Hz
Montserrat: 230V, 60Hz
Voltage difference is within a range many devices tolerate; check your appliance label.