Note: 1 Unfortunately RU (ruby) is not produced in a wide selection of bead shapes and sizes.
I would prefer ruby, except that there are too few choices of ruby in the Swarovski stock list.
Note: 2 The natural birthstones for December are Turquoise and Zircon.
Swarovski does not produce ZI in the round beads as a stock item. I suggest that you substitute ER (erinite) or IND (indicolite) for the ZI (zircon). ER is somewhat bluer and more pale (more like turquoise), while IND is quite close.