Phoenix Star designs a unique freezable bong, Phoenix Star Beaker Bong 5mm Thick Freezable Coil 12 Inches . Both the downstem and the bowl are filled with medical grade glycerin. The high grade glycerin will not expand when frozen. And this glass bong is also equipped with a longer glycerin coil. You can place the freezable glycerin bong in your refrigerator for 1-2 hours or more before you start smoking. Then you can enjoy cooler and smoother hits. Made from premium boros glass,