Pipes with filters are new to me. Back thirty-something years ago, when I bought most of my pipes, you never saw a filter except in "drugstore" pipes. But now they seem to come with a lot of mainstream good-quality pipes. I even found one in a new Peterson!
My first inclination is to toss 'em out -- but if I do decide to use them, how often are these critters supposed to be changed - every smoke? They sure do seem to get soggy and crappy after even only one bowlful. I don't know if that means they're actually doing something useful, or if it proves that they just gunk up the pipe.
Thanks for your expertise.
A lightning flash, a puff of smoke, a phantom, and a pipe dream.
- The Diamond Sutra (slightly edited for pipe smokers)