FOREWORD: a. This bulletin is under the jurisdiction of the Committee on Standardization of Tubular Goods. b. The purpose of this bulletin is to show the formulas used in the calculation of the various pipe properties given in API standards@ including background information regarding their development and use. c. American Petroleum Institute (API) Bulletins are published to provide information for which there is a broad industry need but which does not constitute either Specifications or Recommended Practices. d. Any Bulletin may be used by anyone desiring to do so@ and a diligent effort has been made by API to assure the accuracy and reliability of the data contained herein. However@ the Institute makes no representation@ warranty or guarantee in connection with the publication of any Bulletin and hereby expressly disclaims any liability or responsibility for loss or damage resulting from its use@ for any violation of any federal@ state@ or municipal regulation with which an API recommendation may conflict@ or for the infringement of any patent resulting from the use of this publication. e. This Standard (supplement) shall become effective on the date printed on the cover but may be used voluntarily from the date of distribution. Attention Users: Portions of this publication have been changed from the previous edition. The locations of changes have been marked with a bar in the margin@ as shown to the left of this paragraph. In some cases the changes are significant@ while in other cases the changes reflect minor editorial adjustments. The bar notations in the margins are provided as an aid to users as to those parts of this publication that have been changed from the previous edition@ but API makes no warranty as to the accuracy of such bar notations.