I have the Cutco extendable knife, and IMO it is the BEST knife I've ever used. I've had it for 3 years and have cleaned a ton of fish with it. Haven't sharpened it yet, and I think it's still sharper than my new Rapala knife!Manual.. Pretty expensive but guarenteed FOREVER. The Cutco Filet knives are really nice, hold an edge well, and the rep will come out to my house and sharpen it for free.