Feature: 1. Made of high quality aluminum material, sturdy, durable and long service life. 2. Professional manufacturing, stable characteristics and high reliability. Robust design and manufacture will last longtime. 3. Small size and lightweight, easy to carry and store, convenient to use. 4. This is ideal unit that connect a cylinder to your existing aquarium fish CO2 tank regulator or homebrew beer keg mini regulator. 5. Makes portability of homebrew easy. Great for events so you don't have to drag around a larger tank because of the small size of CO2 tanks, this is not recommended for carbonating, but great for dispensing. Specification: Condition: 100% Brand New Item Type: Pressure Relief Adapter Model: TR21-4 to W21.8 Material: Aluminum Color: Silver Quantity: 1PCS Power: 300W No Load Speed: 30（b.p.m） Air Consumption: （m3/min） External Thread: W21.8 Weight: Approx. 100g Package Size: Approx. 4x3x3cm/1.57x1.18x1.18inch. Package List: 1 x Pressure Relief Adapter 1 x Accessories