A glass pipe with a sliding glass tube inside. You can load it with the amount of cannabis you would in a blunt. The concept is that you burn the end of the pack, and slide the ash out of the end as you smoke.
Can also be used to vaporize, by packing halfway and not letting the flame into the end of the piece.
I was in Venice Beach, and this guy with the sickest chronic loaded 2 grams into a glass blunt... ten minutes later, we were all faded, and no harsh tobacco smoke to ruin the sweetness of the herb.