I bought a couple of sets of aftermarket blades for my new Ferris ztr on Ebay to try out and last night I bent one and laid a nice stripe all around my lawn. Luckily I wasn't at a customer's place. I am in the Texas hill country and it is common to hit rocks and sometimes large sticks from the oak trees hidden in tall grass. The blades I used looked exactly identical to the original Ferris blades but I have a feeling they're not heat treated as well. I didn't have enough experience with the Ferris blades to know how durable they were, but the factory blades on my Deere rider are indestructable. I got a limb lodged between the blade and the deck which bent it down a good inch. Once I got the limb free, the blade sprung right back into place. Are all aftermarket blades junk, or should I just keep trying different sources? I am also going to try some snapper "ninja" blades. They are thin, but my experience on my 21" is they are tough, and mulch like no other.