The Masterplug TAVUK-MP travel plug adapter will adapt any plug to a UK or Irish plug, this includes including US plugs (grounded and non-grounded). Thids is known as a UK Visitor Plug Adapter, because it allows people with non-UK plugs to use a UK socket.
Perfectly safe to use for any appliance that runs on 220 – 240V AV or is Multi-Voltage. This is a plug adapter not a voltage converter, so if you do use US or other 120V country appliances you should only use multi voltage equipment from those countries such as most notebook and laptop computers, tablet computers and mobile phone chargers. Check that your equipment is multi voltage before using this adapter! Often you will find "100 – 240V AC" printed on multi voltage products.
For items from Europe there is no problem as they use the same or very similar Voltage to the UK and Ireland.