Hi Steve, they say pics are worth a thousand words, so here is a brief tutorial on how I made my cheapo gap seals. Indeed the material is simply pipe insulation from the depot or lowes. On my Series 5 , my horizontal stab and elevator tube diameter where the seal is installed is about 1 and 1/4 ", so I used a 1" pipe insulation (I suspect 3/4" would work fine as well). Don't know if all models are this diameter. I needed roughly 8 feet of material to cover all gaps. You don't cut it in half , that would give the wrong shape to the foam. You have to replicate your empennage tubes with a simple cutting jig as shown in the following photos. I had a piece of 1" copper on hand but pvc would work in about a 1'' diameter. Once cut to size , I initially tried to wedge them in place , but test flights revealed that elevator travel and propwash would move them slightly, so I contact cemented them in place to each tube. As the elevator moves up and down the radiused part of the foam roll on each other. When cementing in place , put the seal in place when the cement is still wet so you can reposition them to final position before it dries. I would do the stab seal (forward one) let it dry then the elevator (aft one) so you don't disturb the installed one. Do not know if the gap distance is the same for all Kitfox models so you may have to find the right foam for your installation. Hope this helps Bruce