The RK5121K Sonicrafter features 3.2-degrees of oscillation for fast cutting. The 3.0 amp tools offer significant power while the Universal Fit System and Hyperlock make it easy to change accessories. The RK5121K has variable speed for precision control. It is part of the Sonicrafter Universal Fit System which is a one of a kind Oscillating tool system that works seamlessly with other oscillating tools and accessories. The first half of the Universal Fit System is the Sonicrafter tools that use a Hyperlock blade mounting system that will not only work with all Rockwell Accessories, but it will accept other brand's accessories as well. The Rockwell Sonicrafter accessories are the other half of the Universal Fit System. They have a universal interface that works with other oscillating tools. This allows you to work with any Rockwell blade you want on any oscillating tool you have.