@SplinterGroup they are decently heavy but not enough to contain unruly books. If any of these books had a slouch, they would likely overpower the bookend. They are better suited for small paperback books than the large ones in the photos.
@Pottz They had a few live ones when I cut into them but then I put them in a toaster oven on 300 degrees for a few hours. That took care of them. I have had a few of my larger creations let a few bugs loose though.