Afterburner Matrix Stemless Perc Glass BongAfterburner Matrix Stemless Perc Glass Bong by Weed Star A Stemless Glass Perc by the design guru's over at Weed Star they have made this matrix perc which when smoked diffuses the smoke through all the coolant in the bong giving a cool smoother hit. The narrower mouthpiece is the perfect size for a concentrated hit, add a nail and dome and you have the perfect oil or concentrate rig.