The Petrostar Back-Pressure Valve System is designed primarily for use in Xmas Tree Wellhead Tubing Hangers. This PRS back-pressure valve can be used in conjunction with PRS Nipple Profile. This PRS Back-Pressure Valve has several special features. It has two external packing stacks, one internal packing stack, two internal MTM seals, three shear pin hold-down features, a knockout plug feature, and O-rings in the packing stacks. This PRS back-pressure valve is a high-pressure top no-go lock system. The top no-go provides a position locating means to simplify running procedures and eliminate mis-runs. The PRS back-pressure valve is designed such that pressure from above and below is held by key/nipple engagement. This assembly is designed for H2S service, has Teflon/PEEK packing, Chemraz O-rings, and meets the requirements of NACE MR-01-75.