inner_hole_dia = 6.5;
second_dia = 44;
third_dia = 63;
outer_dia = 83;

thickness = 3;
outer_thickness = 7;

$fn=50;

translate([0,0,thickness/2])
linear_extrude(height=thickness, center=true, convexity=10, twist=0) {
    difference(){
        circle(r=second_dia/2);
        circle(r=inner_hole_dia/2);
    }

    

    translate([0,-25,0])
    square(size=[25, 20], center=true);
}

translate([0,0,outer_thickness/2])
linear_extrude(height=outer_thickness, center=true, convexity=10, twist=0) {
    difference(){
        circle(r=outer_dia/2);
        circle(r=third_dia/2);
    }
}