This is a 4-inch plain downstem from Cheech Glass, the part that carries smoke from the bowl down into the water. It has no percs, just a simple, reliable open design for clean airflow. It fits a 19mm joint on the outer end and takes a 14mm bowl on the inner end, so check those sizes against your bong before buying, since a downstem has to match the piece. The length is measured from the top of the ground joint to the end. It's built in borosilicate glass. A straightforward replacement or upgrade for a broken or mismatched stem.