Deep back thinning has been applied not only to the solid blades but also to each individual tooth of the comb blades. Especially, the solid blades have an astonishingly deep back thinning of 3.5 inches, so a clear cutting edge will last for a long time. 30 teeth/straight blade/thinning rate 40% Ideal for thinning the ends of hair. Please understand that this is a used item and only purchase if you are comfortable with that.