Sigma Fasteners provides quality bolting and coating for the energy industry. Sigma is a manufacturer and distributor of ASTM ... bolting specified by the American Petroleum Institute. Sigma holds an American Petroleum Institute API 20E-0017 Monogram License to manufacture API 20E bolting and is certified API Spec Q1, 9th edition. Sigma Distributes standard bolting and manufactures custom bolts to customer specifications and per print following careful details of the latest revisions. We are ISO 9001 2000 certified and are on the approved vendor list of major wellhead manufacturers, energy and petrochemical companies worldwide. read more