Clover and Fons and Porter makes very sharp seam rippers. I have lots of those to take to classes and sewdays because they are easy to replace. I use the best seam rippers for home. Gingher surgical seam ripper is my favorite. It opens a seam like a zipper. Once you use a super sharp seam ripper the cheap ones will be like cutting with a dull rotary blade. I don't understand having just one seam ripper.