The 90a hardness combines the speed and durability of a hard wheel with the forgiveness of a soft wheel.
About the Skull and Sword artwork:

The Rodriguez “Skull & Sword” deck was the first pro signature deck graphic produced by Powell-Peralta. The graphic was conceived by Ray and Illustrated by V.C. Johnson with art direction from George Powell in 1979.

Initially released in two distinctly different shapes; a 10″ x 30″ “Widetail” version and a 10″ x 28.5″ “Snub Nose,” it came in “Brite-Lite” Dayglo yellow, orange, purple and green. In years to follow, it was made in various different colors and a Powell-Peralta logo was added. In 1983 Ray’s signature was removed and replaced with a Powell-Peralta script logo.