FWIW, I bought my 15K Shapton Pro with 15mm thickness from a very experienced honemeister. He wanted to go with the 16K glasstone @ 5mm honing thinckness. He has since told me that although he likes the 16k glass it doesn't cut any faster then the 15k pro and he feels they are about equal in their performance. So...... get a pro in whatever grit size you desire and cut it without the hassle of dealing with the glass. More bang for the buck with the 15mm.