Pure Glass | 15" Tree-Perc Straight Tube Bong15 Tree Percolator Straight Tube Bong Ice Cold, Ultra Smooth Rips If youre serious about cool, filtered hits, meet the Pure Glass 15 Tree Perc Straight Tube Bongwhere science and smoothness collide. This high performance glass bong is built with an 8 arm tree percolator and a glycerin filled double wall cooling chamber, making every rip feel like it came straight out of an ice cave. Heres how it works: freeze the glycerin chamber, lock it in place,