I believe that is a 3/8 Allen key.
T-60
My 2003 Cavalier uses a 3/8 hex key. It probably should be the same.
I believe that needs a 3/8 Allen or some models, 7mm Allen.
Metric Allen wrench.
You need a 15 mm regular wrench.
It will be a 14 or 17 mm wrench.
45t
use an Allen wrench not a socket or open or box wrench.
14 mm
3/8"
You need a 3/8 Allen Wrench
it's a 3/8 wrench for both 2003 and 2004 caliper.