This is an Apple European plug, also known as the Euro 2 pin, so if you need a spare plug or you are going on holiday or travelling to a European country, then this plug will simply fit onto your MacBook ac adapter and allow you to plug into the European power outlet or any country that has the European standard Euro power sockets.
Connection: 2 hole snap on plug (also known as the Duckhead adapter)
Country electric socket type: Euro (European)
Contents: Apple Euro 2 pin plug
Compatible with: Any Apple MacBook, MacBook Pro, MacBook Air, IPod, Ipad, Iphone, basically any Apple device that has a two hole connector lead or plug that can be removed.
Also available are the UK and US version which are shown below.