Of course, mouthpieces are a highly personal matter. Of course, glass mouthpieces are always special in regards to "playableness". As a player of 13 years now, I couldn't get a proper melody together. This might be the case for me because of the very short but broad tip opening. Be sure you want something this extreme (tip length is cited as 0mm on the website with a tip opening of 1.2mm).
However, it seems to be decently manufactured even though I didn't measure at home. A more experienced player who likes a mouthpiece with extreme dimensions could surely get a lot of fun with it.