shown a cross sectional view of a section of one embodiment of a seal 40 in accordance with the present disclosure in one arrangement the seal 40 may include an upper end adapter 48 a a first unidirectional seal stack 50 a a center adapter 52 a second unidirectional seal stack 50 b and a second end adapter 48 b the end adapters 48 a b and the center adapter 52 may be formed of a material harder or more rigid than the material of the seal rings 54 so that pressure applied to the end adapters 48 a b can be distributed relatively evenly through the seal stacks 50 a b the unidirectional seal ring stacks 50 a b may include one or more cylindrical seal rings 54 the seal rings 54 may be formed as chevron type seal rings as used herein a chevron seal ring is a pressure responsive sealing element that flexes to form a seal against adjacent surfaces the chevron shape may defined by two wings 56 that are hinged at an apex 58 the wings 56 may form an angle less than one hundred eighty degrees the seal ring 54 is responsive to the pressure applied on the apex 58 side i e unidirectional in one embodiment the seal rings 54 may be u201c u u201d or u201c v u201d shaped annular elements formed of a material that allows a predetermined amount of flexure when the ring 54 is compressed thus pressure.