$fit=50;

rotate_extrude(){

difference(){
union(){
translate([10.5,0,0])square([5,7], center = true );
translate([19.5,0,0])square([5,7], center = true );
}

translate([14.75,0,0])circle(3.5);
}
}
for (ball=[0:30:360]){
rotate([0,0,ball])
translate([14.75,0,0])
sphere(r=3.25);
}