NOTE: OK now DELLORTO is no longer making the old style slides that drop right in to the oldest PHF carbies.... They are only making the style slide with the thicker ramp on the bottom where the slide screw touches. What this MIGHT mean for you is that depending on what style PHF carb body you have, there MIGHT be enough clearance for the newer style slide or not. If there is not enough clearance then you must grind off a bit of the inside of each ramp on the bottom of the slide as these ramps are a bit thicker than the oldest style ramps. Measuring between the ramps on these new slides = 25.5mm and on the old style slides the distance between the ramps = 28.7mm. Make sense? You have to modify the SLIDE not your carb. Dellorto doesn't care they want you to buy new carbs - welcome to the world of Italian manufacturing ideals.