They are not proprietary. However, if you custom order socks from a filter bag company, you can order socks that aren't as long or different micron sizes to clean the water better. The company I looked into can make the same sock, but 8" long instead of 14 so it won't drag on the bottom. That way you have less of the dirty muck sitting in the water. May clog faster though.
Anyhow, it's like $3/sock to custom order, but you must order 25 minimum. Great deal and you don't have to worry about running out. I also made my socks 50 micron for my other non-Trigger sump. Keeps it much cleaner.