Ergotec A-Head Stem - CharismaErgotec A Head Stem High Charisma ergonomic and safe. When you choose Ergotec, you choose cycling comfort, stability, and top quality that you can rely on for years. Safety comes first for Ergotec. Ergotec subjects all handlebars stems and seat posts to rigorous testing and classifies them according to a unique safety system, guaranteeing that you'll always be able to select the right parts for your bicycle.