The most popular size for water pipe joints, the 18mm glass on glass joint is not a small connection point. If you are after airflow then this is the size for you. This joint size is the standard for large water pipes but it can be found on smaller tubes as well. Maybe you’re looking for your first water pipe or maybe you’ve already got a drawer full of 18mm bowls and ash catchers. Either way you can browse water pipes by joint size at Brothers With Glass.