A strut bar, which is also known as a stabiliser bar, is usually an aftermarket suspension accessory that aids vehicle handling and provides extra stiffness between the strut towers in high speed conditions. It mounts between the strut towers and reduces chassis flex. It distributes more evenly the tension between the left and right struts of a car. Think about the forces you feel on your body when you turn your car. You feel a push to the outside of the turn and tend to compensate by leaning into the turn to remain upright. Strut bars work in similar fashion by stabilising or sharing that roll tension between the left and right strut.