The AD-15D impact socket set includes 15 impact socket inserts and comes in a metal case for storage and transport. The specialized Adler impact socket sets are designed for use with pneumatic tools that operate under very challenging conditions and varying loads. The socket inserts are made of steel. Cr-Mo steel is a unique alloyed steel with double the tensile strength of regular carbon steel and triple the yield strength. It is particularly recommended for professional tire and automotive service. There are short, long, short plus sets, as well as long power socket sets made of aluminum for rims and individual 1/2" and 3/4" socket inserts.