module hollowCylinder(innerRadius, outerRadius, height, $fn = 360) {
    difference() {
        cylinder(r=outerRadius, h = height, $fn=$fn);
        translate([0, 0, -0.01]) cylinder(r=innerRadius, h = height + 0.02, $fn=$fn);
    }
}

//hollowCylinder(1, 2, 10);