Mazda's use the 6607, which is the same filter as the 7317, but shorter. They are completely interchangeable.
Now that Wal*Mart no longer sells their own ST, I guess I'm going to have to go with another brand.
From a Consumer Reports test years ago, the WIX was the best at that time, and I'm pretty certain they're still real good.
I still have a quite a stock of ST's on the shelf... guess I won't be changing brand anytime soon!