q = 100;
hole_angle = 27;
inner_height = 18;

difference(){
union(){
    linear_extrude(height=2.5){
        difference(){
            circle(d=25, $fn=q);
            circle(d=12.5, $fn=q);
        };   
    }

//    linear_extrude(height=18){
    linear_extrude(height=inner_height){
        difference(){
            circle(d=20, $fn=q);
            circle(d=14.5, $fn=6);
        };   
    }
}

rotate([0, 90, hole_angle]){
    translate([-5,0,-12.5]){
        cylinder(25, 5/2, 5/2, $fn=q);
    }
}
}