One of the highest strength copper based alloys available on the market today is beryllium copper, also known as spring copper or beryllium bronze. The commercial grades of beryllium copper contain 0.4 to 2.0 percent beryllium. The small ratio of beryllium to copper creates a family of high copper alloys with strength as high as alloy steel. The first of the two families, C17200 and C17300, includes high strength with moderate conductivity, while the second family, C17500 and C17510, offers high conductivity with moderate strength. The principle characteristics of these alloys are their excellent response to precipitation-hardening treatments, excellent thermal conductivity, and resistance to stress relaxation.