Soda CO2 Gas Converter Adapter for TR21-4 Female to TR21-3 Male Thread Compatible with Soda Machine Cylinders Good sealing performance, no air leakage when connected to the cylinder, more convenient to use. Primarily used as a thread adapter for soda machine cylinders; can also function as an air source connector. Made of high-quality copper material, high hardness, wear-resistant, and durable for long service life. Tightly machined threads with precise craftsmanship ensure stable performance; installation and use are simple. Allows the use of a sodastream TR21-4 soda bottle in place of a Quooker Cube bottle (adapter required). Threads: TR21-4 female to TR21-3 male. Note: Product may vary slightly between batches; minor differences in color or design may occur but do not affect functionality. Color: As shown in photo Material: Copper Package Includes: 1 x Soda CO2 Gas Converter Adapter Contents limited to the above; other items not included. Note: Lighting effects and monitor settings may cause slight color variations between the image and the actual item. Measurement error allowance: +/- 1-3 cm.