Product enabling safe limiting of the tilt angel of a window. Thanks to the application of the restrictor, it is possible to leave the window ajar tilted by approximately 10cm (depending on a window type and size) without fear that strong wind will change the sash position. In low installed windows, the ZBB restrictor protects against unwelcome full opening of the window sash by children. When the window is closed, the restrictor cannot be seen and does not hinder window operation.