5160 Spring Tool Steel (Knife, Blade) Flat Bar /  2 PIECES /  7 1/2" X 3" X 1/4"  +-

The images are typical of what we have.  It is all about 1/4" thick but tapers a bit so it may be less than 1/4 at one end and more than 1/4 at the other end.

These were heavy duty truck springs.  They have some rust but not very much.