This reduction adapter may be a little piece, but it's big on versatility. This adapter helps you get the most out of your Grav Labs STAX Bubbler Conversion Kit. The conversion adapter is made using the best quality borosilicate glass.  This 34mm to 18mm reduction adapter reduces any 34mm STAX joint to a 19mm joint, to use with 18mm attachments. You can use this reduction adapter to make it possible for you to use the STAX Trumpet mouthpiece on top of any other base or filter in the STAX mix and match series.  34mm to 18mm glass reduction adapter Made of borosilicate glass  Sturdy and durable  Reduces any 34mm STAX joint to a 19mm joint