Abstract: A change-out flange suited for use at an existing head casing of an oil or gas production well. The change-out flange is devised to replace standard hammer caps atop a well casing. By the present invention, with comparative ease a variety of wellhead equipment can be removably and interchangeably secured to the wellhead using an existing casing bowl or spool. The change-out flange has a casing hub that can be screwed unto a known casing bowl, and an integral connection flange provided with a plurality of connection holes arrayed in a manner consistent with the connection hole arrays of an assortment of conventional wellhead devices such as valves. A variety of well head devices thus can be more readily removed from, and securely replaced upon, the change-out flange. Lockdown pins are insertable into the change-out flange in a manner which secures the tubing hanger in place within the casing bowl.