Secondary seals are placed around the production casing stub in the bottom of the bowl of the tubing head. The structure consists of two elastomeric-shaped seals located in grooves in the bottom of the tubing head. A seal is achieved by interference of the seal with the outside diameter of the casing and the bottom of its retaining groove. A spring molded in each inside corner of the seal forms an anti-extrusion mechanism when sealing against pressure. It accomplishes this by bridging the gap between the tubing outside diameter and casing head seal bore. The shape of the seal allows it the flexibility to maintain sealing interference with the large variations in tubing outside of the diameter.