THIS CHAPTER PRESENTS chemical and mechanical properties of two J-55 casings selected to have significantly different yield strengths. The chemical composition and tensile properties of the tested casings met the specification requirements for both J-55 and K-55 casing grades. Consequently, the results of the investigation are equally applicable to both grades. Also presented are the results of burst tests that were conducted at Battelle [1] on short sections of these casings containing milled notches and the results of a failure analysis of the tested sections conducted at the U.S. Steel Technical Center. Finally, the significance of the results to API Charpy V-notch requirements for J-55 and K-55 casings are discussed.