This is the Factory Western / Fisher Gland Nut # 43135.

If you have a fluid seeping out of your lift cylinder at the chrome or at the top of the tank this is most commonly the fix.

If you need the split ring for these cylinders it is part # 43134.

This is the larger 1-3/4" version. 

This uses an o-ring rather than compression packing.

It is used on:

Western lift cylinder 43149, for the MVP3, WideOut (generation 2), WideOut XL, Pro Plus HD. 

Fisher Lift Cylinder 43132 , for the XV2 v plow, Gen 2 XLS plows, HC plows