The Brigham Rock Maple insert reduces tongue bite and gives a cooler, drier smoke. It cannot exactly be called a filter, as it does not impede any airflow to your pipe. Directions: Remove often to shake out moisture, replace with new filter every 2-3 weeks or when discolored dark brown. For longer life, rinse and dry distillator after a couple of uses.
I have them in my two cob-pipes (both are the MO Meerschaum 'Legend', one straight-stem/one bent-stem); they might be a little small for that model, but they fit both with a bit of careful effort. They rinse out easily, and I can also run a pipe-cleaner through them, just to be extra thorough. I like having something I can clean & re-use, and these li'l guys get the job done nicely.
Good filters for pipes are hard and good to find. As I'm very fussy about stuff I use, I expect decent products if they are touted to be good. These filters do an excellent job.
I only smoke cobs so can only speak from that point of view. I find briars have too much juice running back to the stem so don't use them. But the Brigham filters used in the cobs are very good value for money.
When I finish a bowl I take out the bit, dry and clean out the filter and pipe for next time. I think drying the filter with paper towel or similar just gets a fair bit of goozy off it so it goes a bit longer.
Quite a good filter. Excellent value for money.