sight glass(moisture indicator) is a kind of element which shows the moisture and the flow of refrigerant. 

Descriptions

1. The content of refrigerant in the line of the system; 

2. The content of water in the refrigerant; 

3. Indicates the oil level of compressor crooked. 

4. SG-series have indicator paper whose color changes can indicate the content of water in the refrigerant; 

5. The glasses and the "O" ring can make sure there is no leak of the refrigerant; 

6. Max. Working Pressure: 35bar (500psig); 

7. The temperature of the medium: -50 oC - +110 oC; 

8. The content of water is low, the color will change blue while high it will change pink which shows that filter dryer in the system needs to be changed.