I've recently been thinking of purchasing a bong (Percolator Bong Pink - Black Leaf) and the joint size is listed as 18.8mm/14.5mm, what does this mean exactly? In general I know what joint size means, but i'm always confused about things like xmm/xmm, and xmm>xmm. I was also thinking of purchasing a carbon filter (Carbon Filter Adaptor 14.5/18.8), and i'm wondering will it fit, the joint size is (there is only 14.5mm in stock)? Also, do carbon filters filter out THC at all, or anything else in bud that I don't want to be filtered out? Thanks.