Some argue that they don't exist in Ireland.
Workers without fixed hour contracts dread looking at their rosters.
That's according to the Mandate Trade Union which is calling for an end to 'zero hours and 'if and when' contracts.
The Union says tens of thousands of workers in many sectors, including retail, hospitality and the media, don't know from week to week what hours and income they'll have.
But Deputy Editor of The Times John Walsh told Newstalk Breakfast that zero hour contracts don't really exist in Ireland.