I am interested in Diesel Elements 1 418 325 077 1325-077 and 1418 325 159 1325-159 For IVECO/KHD/MAGIRUS-DEUTZ/MERCEDES-BENZ.Can you tell me what is the physical difference between plunger element 1325-159 and 1325-077? Have they different barrel diameter, and if so, which one has the greatest diameter?