Many plastics are in no way strong enough for use in such a device as a set of knuckles, simply because it will undergo a lot of shock and is very susceptible to cracking or breaking. This set however, if printed in plastic, works perfect as a trainer for anyone who does not want to practice their self defense with the real steel version as it may lead to injury for someone who has not used a set of real brass knuckles before. UPDATE- New .stl file has been attached for a more decorative set of knucks still same size DISCLAIMER- Keep in mind that the intended use of this is for training purposes only and should not be used to cause harm or inflict pain in any way. I am not responsible for the negligence of those who do not abide their state or country's laws. Print with 100 percent fill preferably with ABS...pla did come out well though