A hemostasis valve, comprising: a main body (12; 112) having a distal end region and a proximal end region (22; 122); a plunger coupled to the proximal end region (22; 122) of the main body (12; 112), a cartridge (20; 120) at least partially disposed within the proximal end region (22; 122) of the main body (12; 112), the cartridge (20; 120) including a first seal member; a second seal member disposed within the proximal end region (22; 122) of the main body (12; 112); a nut coupled to the proximal end region of the main body; wherein the plunger is configured to be rotated to cause the nut to rotate and move distally which urges the cartridge distally within the proximal end region of the main body such that the cartridge engages and deforms the second seal member, thereby shifting the second seal member to a closed configuration; wherein the plunger is configured to be released or otherwise allowed to move proximally which closes the first seal member while the second seal member remains closed; characterised in that the cartridge (20; 120) has one or more projections (150; 250) formed thereon; and wherein the proximal end region (22; 122) of the main body (12; 112) has one or more recesses (148, 248) formed therein, the one or more recesses (148, 248) being designed to engage the one or more projections (150; 250) to limit rotation of the cartridge (20; 120) relative to the proximal end region (22; 122) of the main body (12; 112) as the cartridge (20; 120) moves distally within the proximal end region (22; 122), wherein the one or more projections (150; 250) are fitted within the one or more recesses (148, 248) and translate along the one or more recesses (148, 248), when axial forces are applied to the cartridge (20; 120) by the nut. a main body (12; 112) having a distal end region and a proximal end region (22; 122); a plunger coupled to the proximal end region (22; 122) of the main body (12; 112), a cartridge (20; 120) at least partially disposed within the proximal end region (22; 122) of the main body (12; 112), the cartridge (20; 120) including a first seal member; a second seal member disposed within the proximal end region (22; 122) of the main body (12; 112); a nut coupled to the proximal end region of the main body; wherein the plunger is configured to be rotated to cause the nut to rotate and move distally which urges the cartridge distally within the proximal end region of the main body such that the cartridge engages and deforms the second seal member, thereby shifting the second seal member to a closed configuration; wherein the plunger is configured to be released or otherwise allowed to move proximally which closes the first seal member while the second seal member remains closed; characterised in that the cartridge (20; 120) has one or more projections (150; 250) formed thereon; and wherein the proximal end region (22; 122) of the main body (12; 112) has one or more recesses (148, 248) formed therein, the one or more recesses (148, 248) being designed to engage the one or more projections (150; 250) to limit rotation of the cartridge (20; 120) relative to the proximal end region (22; 122) of the main body (12; 112) as the cartridge (20; 120) moves distally within the proximal end region (22; 122), wherein the one or more projections (150; 250) are fitted within the one or more recesses (148, 248) and translate along the one or more recesses (148, 248), when axial forces are applied to the cartridge (20; 120) by the nut.