I was given this water filter setup from a parishoner who knows I brew, and I was hoping when I opened it there'd be something identifiable on the cartridges to let me know what I'll need to buy for it, but aside from "MADE IN USA" and "This end up," there's nothing. The cartridges are approx 10" tall and below you can see how they connect to the housing. (They just slide into place and are sealed with the blue rubber rings.
I've always just used tap water filtered through a Britta attachment and am a noob at anything more complex...
(And yes, I know Google's my friend, but I thought I'd toss this out here in case anyone looks at this and can say, "Oh, yeah, of course, that's...")
Here are the pics. Thanks!