Abstract: An adjustment and fixation system can be adopted, for example, for use with a protection vest for two-wheeled vehicle drivers. The system can include: at least a set of a teethed strap (1); a plug-in device (2) of the strap; the strap (1) being composed by several teeth (4) with a quadratic form; a step in quadratic form belonging to the plug-in device (2), that due to its indenture (3), works as a lever, enabling together with the teeth (4), the blocking and/or fixing of the strap movement, enabling the protector's correct fitting. During use, it is only necessary to press the extremity (10) of the device. The system can be configured to enable a more suitable adjustment and fixation for protection vests, so that the same can be adjusted while the driver is in movement.