NEMA published ANSI/NEMA C29.4-2015 American National Standard for Wet-Process Porcelain Insulators—Strain Type. Standard covers insulators used in the transmission and distribution of electric energy, and is used by electric power utility companies, public utilities, and manufacturers of high-voltage electrical products. In this revision, changes have been made to sampling sizes, glaze and color requirements, units of measurement, and marking and packing requirements.