Fully plastic nose bridge. The very hard thread on the mask serves to fix the mask on the bridge of the nose. Therefore, it is also called fully plastic nose bridge strip-nose bridge tendon-nose bridge line. The hard strips of the mask are all made of polyolefin resin. Like metal wire, it bends and deforms with external force, does not rebound when external force is lost, and maintains its existing shape. It can be melted similarly to non-woven materials. , which plays the role of fixing the mask on the bridge of the nose.