The brass ring and white plastic rings are packing around the valve stem (i.e., the part that you pull to turn the water on and rotate to adjust temperature). The brass ring goes in first and the two plastic rings are on the outside. A nut compresses down on white rings to prevent leaks.
Hello Paul and thank you for your question. Both of these model numbers are for the same DANCO Repair Kit for American Standard Tub and Shower Faucet. Best wishes on your project.