A rotary type shaving machine for providing a user selected bristle length, comprising: a) a circular basic grid having a center, a predefined thickness and predefined pore sizes, distances between pores and geometric characteristics; b) a circular and circularly rotatable razorblade having a center and positioned below said basic grid, for cutting hairs that enter through said basic grid; c) an additional circular grid replaceably mountable to said basic grid, said additional grid having a predefined thickness (112A-E) and the same pore sizes, distance between pores and geometrical characteristics as said basic grid; and characterized in that said shaving machine further comprises: d) two centering attachment elements (123, 124) provided with said basic grid and said additional grid, respectively, which, after attachment, are coaxial with a central axis of said basic grid, said additional grid and said razorblade, wherein said centering attachment element provided with said basic grid is a notch or a protrusion to fit a corresponding protrusion or notch in said additional grid; and e) two peripheral attachment elements (133, 134) provided with said basic grid and said additional grid, respectively, for being secured to each other, wherein said peripheral attachment element provided with said basic grid is a notch or protrusion to fit a corresponding protrusion or notch in said additional grid, wherein said two centering attachment elements and said two peripheral attachment elements allow for mutual attachment of said basic grid to said additional grid, in such a way to ensure congruency of pores in said additional grid to pores in said basic grid, and wherein the range of overall thickness of said basic grid and said additional grid is selected from the group consisting of 0.26-0.29mm, 0.27-0.30mm, 0.30-0.32mm, 0.32-0.38mm, 0.38-0.41 mm, 0.41-0.44mm, 0.44-0.48mm, and 0.32-0.44mm, such as to cut the hairs at a predefined user selected distance from the skin, to completely avoid a risk of damaging the skin, for protecting the skin and for keeping religious practices. a) a circular basic grid having a center, a predefined thickness and predefined pore sizes, distances between pores and geometric characteristics; b) a circular and circularly rotatable razorblade having a center and positioned below said basic grid, for cutting hairs that enter through said basic grid; c) an additional circular grid replaceably mountable to said basic grid, said additional grid having a predefined thickness (112A-E) and the same pore sizes, distance between pores and geometrical characteristics as said basic grid; and characterized in that said shaving machine further comprises: d) two centering attachment elements (123, 124) provided with said basic grid and said additional grid, respectively, which, after attachment, are coaxial with a central axis of said basic grid, said additional grid and said razorblade, wherein said centering attachment element provided with said basic grid is a notch or a protrusion to fit a corresponding protrusion or notch in said additional grid; and e) two peripheral attachment elements (133, 134) provided with said basic grid and said additional grid, respectively, for being secured to each other, wherein said peripheral attachment element provided with said basic grid is a notch or protrusion to fit a corresponding protrusion or notch in said additional grid, d) two centering attachment elements (123, 124) provided with said basic grid and said additional grid, respectively, which, after attachment, are coaxial with a central axis of said basic grid, said additional grid and said razorblade, wherein said centering attachment element provided with said basic grid is a notch or a protrusion to fit a corresponding protrusion or notch in said additional grid; and e) two peripheral attachment elements (133, 134) provided with said basic grid and said additional grid, respectively, for being secured to each other, wherein said peripheral attachment element provided with said basic grid is a notch or protrusion to fit a corresponding protrusion or notch in said additional grid,