The late 2002/early 2003 WRX have several different factory combinations of brake pads, making it difficult to shop for upgrades. Here is a year-by-year breakdown to assist.
2002: All 2002 WRXs have a combination of D721 front pads and D770 rear pads.
2003: Starting in July of 2002 (2003 cars were made in 2002), Subaru decided on new brake calipers for both the front and rear, which consisted of a D929 front pad and D1004 rear pad. This created four variants of WRX brake setups:
1. Some early 2003 cars got the 2002 style D721 and D770 setup
2. Some cars got the older D721 front pads and the new-style D1004 rear pads
3. Some vehicles got the new D929 front pads with the older D770 rear pads
4. Some got the new D929s front and D1004 rear setup.
These variants make purchasing brake pads and brake kits complicated; the easiest (and only) way to tell what you have is to remove the wheels and measure the pads. Generally any 2003 WRXs made after July of 2003 have the new D929 and D1004 setup that was used until 2005.
2004-5: All 2004+ WRX Models use the D929 Front and D1004 Rear brake pad setup.
In 06 the WRX went to the FHI 4/2 pot setup D460 Front, D461 Rear
here's a site that has most of the FMSI's and jpegs for most make/models