$fn=150;

union () {
    translate([0,0,3]) {
        difference() {
            cylinder (h=6,d=5.5, center=true);
            cylinder (h=7,d=4.5, center=true);
        }
    }
    translate([0,0, ]) {
        cylinder (h=0.3,d=9.0,center=true);
    }
}