The Harmony Bulkhead Sealant Kit contains a super elastomeric sealant for installing and repairing bulkheads.
I purchased this to seal my bulkhead in my Dagger Axis kayak. The lexel sealant worked well. The instruction sheet references information not present on the tube (temperature range) however this information is easily found in the internet. The cure time was a little longer than expected, but results were great. My bulkhead no longer leaks.
Used this to make gaskets on scotty mounts and rod holders. Also squirted it into the screw holes to seal the screws when installed.