Material: Brass, Copper; Operating Temperature Range: -40 to 80 Celsius; Inner Diameter of Brass Nuts: 6.35mm / 1/4 inch, suitable for connecting 1/4 copper pipes.; Overall Size: 73 x 28mm / 2.87 x 1.1 inch(L*W); Packing List: 1 x Sight Glass Advantage: It provides a clear and convenient view of the refrigerant flow within your air conditioning system. Designed for easy installation, this sight glass can be easily installed in the refrigerant line of your air conditioning system with its standard size. This sight glass is suitable for a wide range of air conditioning systems, HVAC, and refrigeration units, both residential and commercial are applicable. Instruction: Install the sight glass into the refrigerant line. Observe the sight glass during operation to check if the flow and the condition of the refrigerant are normal or not. Green means no high moisture in refrigerant. Yellow means the moisture content is too high in refrigerant. Application: This product is widely used in air conditioning and refrigeration systems to monitor refrigerant flow. By using this sight glass, you can inspect the refrigerant levels, identify any potential issues like low refrigerant charge, and take necessary actions to maintain the optimal performance of your central air conditioning system. Note: Please check the size carefully before purchasing.