Rebuilding my 1981 R100RS (+EML) carbs. Ordered new slides (BMW) and found the new ones had an additional shoulder below the diaphragm mounting flange (which was also configured differently, bottom) and a good sized O-ring. The O-ring does not seem to make a soft contact as the slide moves into the closed/low position. The slide still bottoms on the shoulders on either side of the carb throat. Thought maybe the ring was for shipping protection but the slide had a carboard tube around it and the needle for shipping protection. Haven't gone through my various airhead carbs lately so I've probably missed some update info but anyone have any ideas on the whats & whys of the changes? Picture; Left = old, Right = new

---oops!