This part states the procedure for ordering Standard Reference Materials (SRM's) issued by the National Institute of Standards & Technology. SRM's are used to calibrate measurement systems, evaluate measurement methods, or produce scientific data that can be referred to a common base. NIST Special Publication 260, “Catalog of NIST Standard Reference Materials,” lists and describes the SRM's issued by NIST. SP 260 is periodically revised to include new SRM's and eliminate those that have been discontinued. Between editions of SP 260, supplements are issued that list new or renewal SRM's not listed in SP 260. In addition, these supplements list the fees charged for available SRM's.

The SRM's are listed by category in SP 260 and by sequential number in the supplements. The number uniquely identifies a particular SRM. Renewals are indicated by the addition of a letter to the original number. Thus, 11a is the first, 11b the second, and 11c the third renewal of SRM 11, Basic Open-Hearth Steel, 0.2 percent carbon. In this way, a particular number or number and letter always represent a material of fixed or approximately fixed composition.

When new SRM's or renewals of old ones are issued, announcements are made in SP 260, its supplement, and in scientific and trade journals.