“DG” Seal:

Dynamic seal: Carbon
Stationary seal: Silicon carbide.
This seal utilizes the standard “D” type rotating components but has an added stationary seal of silicon carbide for added wear resistance.
The standard stationary seal material is silicon carbide. This stationary seal is reversible, you can changeover very quickly if one side is damaged. 

• Suitable for sanitary applications, including those using non-lubricating and abrasive fluids.
• Silicon carbide vs. carbon is the best combination of seal faces for most applications since its coefficient of friction is very low.