USED FOR PLANTS - PLASTIC BOX FOR PRODUCTION. I have not tried these bits on anything but plastic. So this review is based solely on my experience punching holes in plain clear plastic lids. Even a 10 year old can easily punch holes in plastic with this. Yes, with supervision. I've used them for air holes on my propagation boxes for plant cuttings Since my niece is also interested in plants, I took the opportunity to teach her how to use a drill which "hooked" into just 0.5 mm and went through the plastic like clockwork! the circle was smooth! no rough edges at all. would buy again.