Quantity: 20 piecesColor: BlackCheck Valve: T-shaped structure with a straight channel for air passage. Ideal for use in aquariums, fish tanks, aquaculture, gardening or drip irrigation systems.Compact Size: 3.8cm (D) x 2cm (H). Fits standard 0.4cm inner diameter air tubes. The layer on each joint makes it tightly connected to the pipe, effectively preventing slippage.Free Adjustment: Simply turn the knob to adjust the airflow from closed to fully open. Due to the texture of the knob surface, it is non-slip during use.RELIABLE PLASTIC: Made of durable and healthy plastic for long-term use without any bad effects on your lovely fish. Very lightweight and requires no effort to set up.Easy to Install: Cut the air tube into two sections and insert it directly into the air control valve for connection. Turn the knob counterclockwise to open and clockwise to close.Good quality product