$fn=48;

d0=27.6;

d1=30;

hgt=5;

//5;10

d2=24;

//10;24

dx=1;

difference(){

cylinder(h=hgt,d=d1);

translate([0,0,dx]) cylinder(h=hgt,d=d0);

translate([0,0,-dx/2]) cylinder(h=hgt+dx*2,d=d2);

translate([0,-d1/2,dx]) cube([dx,d1,hgt]);

translate([-d1/2,0,dx]) cube([d1,dx,hgt]);

}