A device, such as a valve, includes a hard seat having an axial bore extending along a central axis. A flapper pivotally connected with the hard seat at a hinge axis and pivotal between an open position to allow flow through the bore and a closed position to block flow through the bore, the flapper having a flapper sealing surface that slopes inward toward the central axis along a full circumference of the flapper sealing surface and the hard seat having a hard sealing surface that slopes inward toward the central axis conforming to the flapper sealing surface and on which the flapper sealing surface bears when in the closed position.