A 9028-02 1/8 inch BSPP (British Standard Pipe Parallel) countersunk plug with seal is a type of threaded plug that is used to close or seal off a BSPP threaded port. The plug has a flat or countersunk head that sits flush with the surface of the port, providing a smooth, low-profile finish. The seal on the plug provides a tight, leak-free seal to prevent fluid or gas from escaping from the port.