Abstract: An annular elastomeric seal, a piston utilizing the seal, and a fluid cylinder assembly utilizing the seal. The seal includes an axially forward portion defining a circumferentially inner and a circumferentially outer deflectable lip seal and an axially rearward portion defining a circumferentially inner and a circumferentially outer arcuate heel seal. When positioned in an annular groove in a piston and with the piston slidably received in the bore of a cylinder, the annular seal provides fluid pressure sealing at the deflectable lip seals, provides secondary fluid pressure sealing at the arcuate heel seals, provides air sealing at the arcuate heel seals, and functions at the arcuate heel seals to preclude the entry of contaminants into the sealing interfaces. The seal is especially effective when employed in a hydraulic pressure cylinder of the center feed type since it allows the usage of a single annular seal positioned in a singular annular groove in the piston.