[About Nutsert] The inner and outer nut are mainly used for the conversion of the internal and external threaded connection, one end has an external thread and one end has an internal thread. One end of the external thread is connected with the internal threaded pipe or the large diameter pipe, and one end of the internal thread is connected with the small diameter pipe, and the internal and external thread can be used. Conversion of internal and external threaded connections, or reduction of pipe diameter.