A straight tube bong closed at one end with a stem and a bowl for your weed. You add water to the straight tube bong, enough to cover the bottom of the stem, and weed to the bowl for a simple, straightforward smoke.
Traditionally a great table top piece, the straight tube bong usually has a little bit less volume than a beaker bong, which can be better for lung capacity. Some folks think that bongs with straight tube are more prone to tipping than their beaker base counterparts - but this is just a myth. Most straight tube bongs have great pedestal bases which are extremely secure bases.