In this photo you can see the effect of heating the tarp clamp pipe section while it is snapped over a piece of standard schedule 40 pipe. All the pipe is 3/4 inch. The thin section starts at the same diameter as the schedule 40. The tarp clamp section was snapped over a section of regular pipe and heated with a heat gun to expand it. It's a tight fit over the standard pipe but once heated the fit relaxes and it cools quickly so the inside diameter of the tarp clamp section is the same as the outside diameter of the standard pipe. The ends flare a little which helps with instalation over the tarp and pipe.