Sovereignty Glass out of California is a pioneer of the industry and creator of some of the cleanest, most functional production glass ever. The stemline series comes in an up gridded or down gridded version where the gridded holes will be on the top or bottom of the perc, respectively. The placement of the grids in the upgrid version allow the bubbles to form more easily and very uniformly above the perc, which gives an overall smoother feel to the pull and a more purr-like hit great for oil vaporization. The downgrid on the other hand makes the bubbles form lower and have to travel further through the water, bigger bubbles are formed and it gives a more chuggy hit that works great for combustion.
Take a look and decide for yourself!
Below is a slow-mo video of an upgrid for your viewing pleasure as well!