A novel centimetre scale tip tilt piston mirror mechanism has been designed in silicon. The mirror consists of three identical mechanism parts and one mirror part. The fabrication of the parts was done with photolithography and Deep Reactive Ion Etching and they are presently being assembled. The originality of the proposed concept resides in breaking down of the kinematic structure into three identical planar flexure-based monolithic structures and the isostatic alignment concepts used to assemble these planar structures into a three dimensional structure.