its a 17mm, its not that hard to remove it, the only hard thing about replacing this line is when after u have disconnected it and to take out u have to wiggle it through those angles at that gap near the pump. I did it in my driveway and had my dad help me to wiggle it only. It should be a 17mm but it has been over a year so i could be wrong. Yea, like Cuel said, put back the bolt after u had taken out the old one so dirt and other stuff wont get into the system, good luck