For those who are not quite sure, the stem is the component on a bicycle that connects the steerer tube of the bicycle fork to the handlebars. Road bike stems have a design that belongs to either a threadless or quill system. For the unashamedly extrovert enthusiast the stem could even be classed as the equivalent of the statuette on the front of a Rolls Royce! It serves a very important purpose too.
The newer style of road bicycle stems is the threadless system. As opposed to inserting into the steerer tube, the threadless system clamps around it. It is now the more popular and has become the industry standard on sport bikes. One of its main advantages is that it allows the user to swap or mix and match stems depending on need. It works well with carbon fibre or aluminium alloy steerer tubes thus making for a lighter overall bicycle.
The older, more traditional road bike quill stems insert directly into the steerer tube with one great advantage being that it allows the cyclist to adjust handlebar height without removing the stem. The majority of utility bikes and the less expensive sport bikes feature the quill system as the norm.
Again, as with all contemporary bicycle technology, road stems offer a high strength to low weight ratio that increase both durability and performance. They are often constructed of aluminium but may be made from steel, titanium, scandium or carbon. And, of course they look good.