Pretty much any 19 stem works fine with the P80. I've used RBT 19/19s, Tanks, Nubs, bendy stem, @Vlad the Inhaler 's terrific vigreaux cooling stems, StemPod stems. All work fine. It's a bit more flexible than with some RBT vapes that will only take 19/19s. Lately i've been using @funkyjunky 's...