Hey makarov666, While there is no absolute minimum size, we recommend targets be at least 5 inches (or 12 cm) wide for a good AR experience. Smaller targets can still be detected and tracked, but the experience will be dependent on factors such as lighting, distance to the camera, and image quality. This article goes over more information related to optimizing target tracking and includes a section with more details on target size: https://library.vuforia.com/article...-Target-Detection-and-Tracking-Stability.html Thanks!