Get the Stainless Steel Anti-Theft Catalytic Converter Protection by MILLERCAT. It's heavier then the cheap aluminum ones. And stainless steel is harder to cut through. Code: https://catshield.com/collections/toyota-prius-gen-3-2010-2015/products/stainless-steel-millercat-2010-2015-prius-gen-3-cat-shield https://catshield.com/collections/toyota-prius-gen-3-2010-2015/products/stainless-steel-millercat-2010-2015-prius-gen-3-cat-shield .
Spot weld nails as spikes all over it. Even if they steal it, good luck trying to sell it and explaining the nails. Also wrap barbed wire around it. If you cant get your hands on some, you can try razors tied to mig wire. Be creative.
You can also use promo code azusa over at catshield.com that was mentioned on post #8 Save some cash to save your cat!!!