4/5 as the plastic ring doesnt really roll with the blade

my lawn mower blades alwasy need sharpening got to the point i just started replacing them for 20$ a pop every few months. Lots of sticks rocks and roots around lol. I had enough so i bought this little guy 2pack and it worked very well for what i wanted. the angle of the stone was pretty much the same as my blade so i just rolled it across the blade a few times than used a file to remove any Burs on the back. make sure to balance your blade do not just sharpen it and toss it back on always make sure its even cause if its not you will vibrate the motor and kill your mower. balancing is easy done with heck a pair of needle nose pliers just place anthing in the center bolt hole and see if it leans one direction or the other if one side is too heavy sharpen that side a little till you have a less of a tilt than your good to go.