The Brass Packing Nut is used in the DELTA/DELTAI, A200/A200I, A2000/A2000I Fiber Instruments. When properly tightened, this ensures that the packing materials create a seal and prevent leaks from the vessel into the interior cabinet. 

For the A200/A200I instruments, refer to Service Procedure Packing and Agitator Replacement (FS004) shown below.
For the DELTA and A2000 instruments, refer to Service Procedure Packing and Agitator Replacement (DES002) shown below.