aldecaker, no, that didn't cross my mind, but I'm sure it's fool proof.
bernie2, those cobs will have some wood in the stems that you could trim off or just burn off...sometimes the stems are slightly twisted, too. They'll all smoke great. The filters will catch a lot of moisture and do make the draw more 'sip friendly' when they're still new. I don't use em, but I have.
I'm still in the 'big idea' mode of doing something about filling those filter stems shanks and making a more traditional airway...on the order of 5/32 "
There are some stems available for the MM pipes that people rave about, and they cost more than the pipes, most of em...the Freehand is kinda costly for a cob, but it's a beaut of a pipe. It comes with a semi polished vulcanite stem, if I'm not mistaken. It's definitely an upgrade from the plastic stems. I like the plastic ones though, because they're soft.
That also is their downfall. I tend to close them up through clenching, but I heat them and open them back up.