The stem is the component on a bicycle that connects the handlebars to the steer tube of a bicycle. Depending on the type of headset the stem either clamps onto the steer tube or inserts into the steer tube and is held into place with a wedge. This racing bicycle is built using lightweight, shaped aluminium tubing and carbon fiber stays and forks. ... The headset is the component on a bicycle which provides a rotatable interface between the bicycle fork and the bicycle frame itself. ...

Stems normally have two dimensions: an angle and a length. The angle is normally 90° giving a slight up angle or 73° which causes the stem to be nearly parallel with the ground. The length of the stem then determines how far forward of the steer tube the handlebars are.

On older stems, the handlebars were slipped into a hole on the end and then clamped into place with a single screw. On newer stems, two screws and a separate plate hold the handlebars in place, allowing the handlebars to be removed without having to remove the brake levers.