A circular stapling device, comprising: a handle assembly; an elongate body that extends from the handle assembly; a cartridge assembly mounted on a distal end portion of the elongate body, the cartridge assembly including: a housing; a pusher member supported within the housing and being movable between a first position and a second position; a retaining ring member supported on the housing and being configured and arranged to move between a radially constricted condition and a radially expanded condition in response to movement of the pusher member; and a fastener cartridge body supported on the housing and having a tissue engaging surface that extends to an annular edge; and a circular cartridge buttress member having a body portion and an extension portion, the body portion being supported on the tissue engaging surface of the fastener cartridge body, the extension portion extending from the body portion and over the annular edge of the tissue engaging surface, the retaining ring member securing the extension portion against at least one of the fastener cartridge body and the housing when in the radially constricted condition, the retaining ring member releasing the radially extension portion when the retaining ring member moves to the expanded condition in response to a movement of the pusher member from the first position to the second position so that the body portion of the cartridge buttress separates from the tissue engaging surface of the fastener cartridge body, wherein the pusher member includes at least one ramp feature extending radially outward from an outer surface thereof, the at least one ramp feature moving the retaining ring member toward the radially expanded condition when the at least one ramp feature engages an inner surface of the retaining ring member. a handle assembly; an elongate body that extends from the handle assembly; a cartridge assembly mounted on a distal end portion of the elongate body, the cartridge assembly including: a housing; a pusher member supported within the housing and being movable between a first position and a second position; a retaining ring member supported on the housing and being configured and arranged to move between a radially constricted condition and a radially expanded condition in response to movement of the pusher member; and a fastener cartridge body supported on the housing and having a tissue engaging surface that extends to an annular edge; and a housing; a pusher member supported within the housing and being movable between a first position and a second position; a retaining ring member supported on the housing and being configured and arranged to move between a radially constricted condition and a radially expanded condition in response to movement of the pusher member; and a fastener cartridge body supported on the housing and having a tissue engaging surface that extends to an annular edge; and a circular cartridge buttress member having a body portion and an extension portion, the body portion being supported on the tissue engaging surface of the fastener cartridge body, the extension portion extending from the body portion and over the annular edge of the tissue engaging surface, the retaining ring member securing the extension portion against at least one of the fastener cartridge body and the housing when in the radially constricted condition, the retaining ring member releasing the radially extension portion when the retaining ring member moves to the expanded condition in response to a movement of the pusher member from the first position to the second position so that the body portion of the cartridge buttress separates from the tissue engaging surface of the fastener cartridge body, wherein the pusher member includes at least one ramp feature extending radially outward from an outer surface thereof, the at least one ramp feature moving the retaining ring member toward the radially expanded condition when the at least one ramp feature engages an inner surface of the retaining ring member.