It's a more expenisve knock-off of ...
the Snake River Electronics AcuGage, Deb...and yes, it does work on any material except metal, by measuring the resistance between the foil strips on the outside of the tank. Raritan has only recently introduced theirs, and I'm a great fan of Raritan products...the quality of everything they make is outstanding. However, Snake River has been making this type of gauge water and holding tanks for more than 20 years, and I've seen many installations nearly that old that are still working--something I can't say about about any gauge that uses an internal sender. You might want to check their website (www.snake-river.org) and even e-mail Dennis Fierello (Snake River's sales manager) with any questions about the differences between the two brands.