Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Didn't find this good for really dull knives

I wish I could write a rave review on this product, but I can't. I will say the device is lightweight, has a great design and is easy to use, but I found the product to be ineffective on sharpening really dull knives. The directions I received with the sharpener also stated that extremely dull knives may need additional professional preparation. I used this product on dull old Chicago Cutlery and Henckels knives and received little results.