seals of opposite orientation are used for a single seal assembly however seals of differing dimensions can be used in pairs without departing from the spirit of the invention alternatively an upper seal 82 can be used in combination with upwardly oriented chevron seals of the prior art disposed below o ring 78 and still be within the purview of the invention alternatively either of the upper or lower seals 82 or 80 can be provided with a back up seal section such as 64 or neither one of them can include this feature all without departing from the spirit of the invention in the preferred embodiment the extrusion rings 54 and 86 can be made from peek while the preferred material for the upper and lower sealing elements 82 and 80 is a composite including 15 glass fibers with 5 molybdenum disulfide ptfe known as moly glass this formulation is commercially available from tetralene inc and sold under the product name comp 115m the material for the extrusion rings 54 and 86 is commercially available from greene tweed inc under the product name peek while o ring 78 is illustrated to separate upper sealing element 82 from lower sealing element 80 the two sealing elements can be placed adjacent to each other without a spacer or with spacers of different sizes or shapes without.