$fn=150;

difference() {
    union() {
        cylinder(d=30, h=55);
        translate([0,0,55]) cylinder(d=25.4, h=28, $fn=6);
        translate([0,0,55]) cylinder(d1=30, d2=10, h=10);
    }
    cylinder(d1=15 * sqrt(2), d2=13 * sqrt(2), h=30, $fn=4);
}