What is the size of the slip-fitter that goes on a round post/pole?

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• I bought a 3 in. round lamp post like you said. But it seems too “small” for the lantern. (I.E. gaps in between.) Why?
• Is the lantern enclosed? Can bugs get inside the lamp?
• Will this light fit an older post that measures 3-1/4 to 3-3/8 in.?
• How do you install the Bentham Post Lantern on a pole?