This bracket / mount assembly is made of 3 pieces and requires (2x) stainless steel, worm gear-style hose clamps per assembly. 

(My hose clamps were 9/16" wide) (There is clearance space on the model for some wiggle room) 

The ID of the pipe clamping side is 1.675" Dia. 

The ID of the square fence post side is 3.450" SQ. 

I am using 2x of these supports to hold a pipe upright, to be used to support a starlink antena. 

I went with this design as it is apartment balcony friendly, no hardware or permanant marks left.