A valve (200, 400) for controlling fluid flow, comprising: a valve body (202, 406) defining: an inlet port; an outlet port; and a flow control aperture that fluidly couples the inlet port with the outlet port; a bonnet assembly, the bonnet assembly comprising: a first bonnet (210, 402) comprising a first closure member; and a second bonnet (216, 404) comprising a second closure member (258, 418), wherein the first bonnet and the second bonnet are substantially coaxially opposed; a seat ring positioned at least partially within the flow control aperture, the seat ring defining a first seat within the valve body that is configured to sealingly engage the first closure member; and a second seat (278, 408) within the valve body and opposite the first seat, wherein the second seat is configured to sealingly engage the second closure member, characterized in that the second seat is positioned at least partially within the flow control aperture defined by the valve body; and wherein the second closure member (258, 418) comprises a compliant seal, and during normal operation when the second closure member (258, 418) is not in use, the compliant seal is positioned within a bore of a cage or a guide of the second bonnet (216, 404) to substantially prevent fluid flow through the valve from affecting the compliant seal. a valve body (202, 406) defining: an inlet port; an outlet port; and a flow control aperture that fluidly couples the inlet port with the outlet port; an inlet port; an outlet port; and a flow control aperture that fluidly couples the inlet port with the outlet port; a bonnet assembly, the bonnet assembly comprising: a first bonnet (210, 402) comprising a first closure member; and a second bonnet (216, 404) comprising a second closure member (258, 418), wherein the first bonnet and the second bonnet are substantially coaxially opposed; a seat ring positioned at least partially within the flow control aperture, the seat ring defining a first seat within the valve body that is configured to sealingly engage the first closure member; and a second seat (278, 408) within the valve body and opposite the first seat, wherein the second seat is configured to sealingly engage the second closure member, a first bonnet (210, 402) comprising a first closure member; and a second bonnet (216, 404) comprising a second closure member (258, 418), wherein the first bonnet and the second bonnet are substantially coaxially opposed; a seat ring positioned at least partially within the flow control aperture, the seat ring defining a first seat within the valve body that is configured to sealingly engage the first closure member; and a second seat (278, 408) within the valve body and opposite the first seat, wherein the second seat is configured to sealingly engage the second closure member, characterized in that the second seat is positioned at least partially within the flow control aperture defined by the valve body; and wherein the second closure member (258, 418) comprises a compliant seal, and during normal operation when the second closure member (258, 418) is not in use, the compliant seal is positioned within a bore of a cage or a guide of the second bonnet (216, 404) to substantially prevent fluid flow through the valve from affecting the compliant seal.