The AISI (American Iron and Steel Institute) was the originator of the 300 and 400 series numbering system (i.e., Type 304 stainless steel). They also published a Stainless Steel products manual that listed these designations and the chemical analysis as well as most mechanical and physical properties of each individual grade. They are NOT specifications as such, just definitions of the individual grades. Most specifications that are used with stainless steel are from the ASTM (American Society for Testing Material). See "Specifications for Stainless Steel" for more information. The Iron & Steel Society took over from the AISI in publishing the Stainless Steel Products Manual a number of years ago.