Here's a strange one for you. I have an Echo PE-200 edger which I have been using all season with Echo blades. A couple of weeks ago I went to the lawn equipment store to a buy couple of replacements. They didn't have any Echo blades in stock, but did have some Stihl, which they buy in bulk. They said they were the same any would work fine. I went ahead any bought a couple. About three days after I put the first one on, the edger started vibrating wildly. Turns out the Stihl blade had worn unevenly and was now out of balance. I put the second one on, and the same thing happened. Has anyone experienced this? I will be darned to know what's happening.