1. This adapter is compatible with all water machines featuring a TR21-4 interface and is designed for connecting an external carbon dioxide cylinder or tank. 2. The integrated design and enhanced internal sealing structure eliminate the need for sealant, improving safety and durability. 3. Equipped with an 8 mm male quick-disconnect fitting for easy connection to standard female couplings; ensures a secure, leak-free connection. 4. Constructed from high-quality metal with a matte surface oxidation finish for improved aesthetics, strength, and reduced weight. Note: Installation instructions are not included. Professional installation is recommended. Please verify compatibility carefully before purchase. Note: Product appearance or color may vary slightly between batches due to manufacturing updates. These variations do not affect functionality. Color: Silver Material: Metal Package Contents: 1 x Carbon Dioxide Filling Adapter Note: Only the items listed above are included. Note: Color representation may vary slightly due to lighting and screen settings. Measurement tolerance: ±1–3 cm.