you are right about two styles. a couple years ago I lost one and got a replacement off of ebay. I noticed the grips were different but didn't notice the location of the valve stem. My understanding is the early 70 caps had poor gripping and they changed the design. My z came with the updated design but the replacement is the early design. Just last month I had a tire company put in longer stems and they put the caps back on. Woe is me for not checking their work. First drive around town lost one of the originals again. Well, now I'm looking for two caps instead of one. Thanks for the info.