It's a really simple matter to get under the vehicle and try different wrenches on until you find the correct one. Most calipers are held on with a 7/'16 bolt, but some are 3/8, some 10 mm and some are even allen or torx heads.
7mm Allen wrench
9mm Allen wrench
it's a 3/8 wrench for both 2003 and 2004 caliper.
9mm
The Allen wrench size for the front caliper slide pin bolts is 3/8".
Metric Allen wrench.
It would be either a 15 mm wrench or a 7mm Allen key.
It takes a FA12A Allen wrench.
T-60
10mm
That's a 7mm Allen key.
3/8 inch allen.