These stems are very similar to Cambridge's #3077 stem. The 3075 stem has a bulge at the bottom of the stem while the 3077 has a completely straight stem. The blue stem shown is #3075.
Another variation shows up and it then becomes the #3085 stem. The Pomona Green goblet in this line is shown above. With the exception of the footed and flat tumblers, all these have identical bowl shapes and sizes. The stemware is distinguished by the length of the actual stem and the No. 3085 line having a much shorter stem as well as somewhat larger knob.
*Note Pomona Green was called Avocado by collectors but in 2010 it was discovered that Henry Hellmers' Cambridge color batch book called the color Pomona Green. Items have also been found with Pomona Green noted on the label. Collectors will probably still call it Avocado but now we know Cambridge called it Pomona Green.