It was a 16.. I got 3 of them out and changed ok but the fourth was a right pain to get out and when i finally managed to prise it out, the little top hat on the end of the injector which the real sits in was missing so i'm assuming its in the head :s so i've taken the spark plug out to try and fish it out with a magnet and in the meanwhile i've ordered a new set of merc injectors.. So no it didn't go ok ha..