these look exactly like my Pentair AF-94 'single' filter module, except that the previous owner has glued multiple units in line. If my guess is correct, all of the currently available pleated filter cartridges and other parts for the current line of 'single' modules should work in your older modules !!! Also, today you can get a Pentair canister top which would convert one of your canisters to n 8 watt UV
unit, purchase a filter insert with a dedicated space for granulated carbon, purchase a canister top meant to allow you to insert a tank heater through the center of the cap etc. ( purchased as parts of course)
check out http://www.drsfostersmith.com/Produc...All&Nty=1&pc=1
If you're wondering how all of the different 'innards' can be configured, there are some blow-up pics of my own Pentair filter setup at http://cloudytanks.com/reviews/howto/pentair.htm
PS you really lucked out running across these canister filter modules !!! The Pentair is the best filter setup that I have ever owned !