Control module mounted on handlebar of bicycle

A control module, which is mounted on a handlebar of a bicycle, comprising:

• a base having a hole, wherein the hole has a first section and a second section;
• a diameter of the second section is bigger than that of the first section;
• and the base is fitted to the handlebar whereby a sidewall encircling the first section touches the handlebar;
• a grip, which is fitted to the handlebar, having a portion received in the second section of the hole of the base;
• at least a control bar pivoted on the base;
• and
• at least a bolt provided on the base, wherein the first section is on the handlebar and the second section is on the grip while the bolt is tightened;
• wherein the second section of the hole is a full circle, and before the bolt is tightened, the grip is able to rotate relative to the base when the portion of the grip is inserted into the second section.