1. Good sealing performance, no air leakage when connected to the cylinder, more convenient to use. Mainly used for threaded joints of machine cylinders, and can also be used as air source switches. 2. Made of high-quality materials, high hardness, durable and wear-resistant, and long service life. The threads are tight, the workmanship is exquisite, the performance is stable, and the installation and use are simple. Color: Gold Material: Copper Package Contents: 1X Thread Conversion Adapter Female Tr21-4 to Male Tr21-3 Only the above package contents, other products are not included. Note: Light reflection and different monitors may cause the color of the items in the pictures to be slightly different from the actual item. The measurement allowance is 1-3cm. Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.