I bought one of these to try out, because I don't like the idea of hot metal particles sitting in my lungs and I was glad to find these. I used it for a long while and liked it and was going to re-order for me and a gift for a relative. There are 6 holes and they are larger than the metal holes. I personally don't mind the larger holes ( not too good for keef however, but okay for hash) as I can't tell the difference in the draw. The larger holes are easier to keep clear and I found there is no difference in the cleaning. Metal or glass. Oh, my bowl was and still is intact - after many cleanings.
I love the glass bowl just a bit thin and cracked
Not many holes, doesn't have same pull like the metal one that comes with it,