The Series 100 is a constant speed tool – 35,000 RPM. The tool itself is an economical option that allows the use of accessories that require a high speed. A key application that generally requires high speed is a fiberglass reinforced cut-off wheel. Using that at a slow speed will make the accessory less effective. There are high speed rotary tool accessories in our line that we do not recommend using with the Series 100 because the accessories require a lower speed for safe operation. Always check the speed rating on an accessory before using it in the tool.