I've got the duosharp two-sided stones, course/extracourse and fine/extra fine. For reprofiling or fixing a very dull or damaged edge, you will save a lot of time by getting the course stone set. Also, there is some misinformation out there that the diasharp (continuous diamonds) are faster, and that the duosharps have less diamonds to save money. That is incorrect. In fact, due to the holes, the duosharps are faster.