$fn = 50;
height = 10;

durchmesser = 45;
thickness = 10;


difference() {
    cylinder(height, (durchmesser+thickness)/2, (durchmesser+thickness)/2);
    cylinder(height, durchmesser/2, durchmesser/2);
    translate([30,0,height/2]) cube([50,30,height], center = true);
}