dottiewarden - I’ve now had a bout 5 bowls pass through my Brigham and I normally take out any stinger or filter system I encounter but the rock maple seems to actually work. I should get some new ones, i’ve just been rinsing the one which was in the pipe when I rescued it from the antique shop haha. Still looks mint after a hot water rinse and dry time - I wonder if the filter is as old as the pipe which I dated to the post patent era 1950’s early 60’s.