The most common type of flagpole installation is the in-ground foundation sleeve method which calls for 1' of the flagpole to be encased in the ground sleeve for each 10' of exposed flagpole height.
The diameter of the sleeve should be atleast 2" greater than the outside diameter of the flagpole with the area between the flagpole and the sleeve filled with dry sand.
These sleeves include a base plate, support plate, grounding spike & steel centering wedges
