According to another embodiment of the invention, the pockets are defined by inturned edges on the covers which embrace a boundary of a recess formed in the surface of the movable element exposed to {TAIL ~ hot gases} of {HEAD ~ combustion} 
According to another embodiment of the invention , the pockets are defined by inturned edges on the covers which embrace a boundary of a recess formed in the surface of the movable element exposed to { TAIL ~ hot gases } of { HEAD ~ combustion }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD