Pressure display of concave-convex figure-eight blind plate: concave-convex figure-eight blind plate: PN 1.6MPa BLF, concave-convex figure-eight blind plate: PN2.5MPa BLF, concave-convex figure-eight blind plate: PN4.0MPa BLF, concave-convex figure-eight blind plate: PN 10.0.