h=145;
r1=5/2;
r2=4/2;
th=1.5;
ct_z=5;
ct_xy=r1*4;
difference ()
{
  difference ()
  {
    difference ()
    {
      cylinder(h, r1+th, r2+th, center = true);
      cylinder(h+1, r1, r2, center = true);
    }
    translate([0, r2+th, 0])
    cube([8*th, 3*th, h+1], center=true);
  }
  union(){
    translate([0,ct_xy/2,+h/2-5])
    cube([ct_xy,ct_xy,ct_z], center=true);
    translate([0,ct_xy/2,0])
    cube([ct_xy,ct_xy,ct_z], center=true);
    translate([0,ct_xy/2,-h/2+5])
    cube([ct_xy,ct_xy,ct_z], center=true);
  }
}