Hey, i bought this bubbler for $10, and it works fine. https://www.dhgate.com/product/glass-tool-mouthpiece-stem-water-bubbler/401291708.html I was poking around the inside and I felt the tubeinside the glass bubbler. It feels plasticy. When I tap it, it makes a different sound then the outer glass part. Does anyone know if its supposed to sound and feel different? Cuz if it isn't glass, this might change how I clean it.