Drilling Structures International, Inc.Drilling Structures International, Inc. (DSII) has been providing quality sales and service to our customers for over 30 years. DSII is devoted to achieving customer satisfaction in the detailing and manufacturing of your fabrication needs through experience and modernization.DSII is an A.P.I. 4-F manufacturer of derricks, masts, substructures, crown assemblies. We at DSII are confident in our ability to find a solution that fits your company�� requirements with our inventive designs and extensive facilities.