This diamond hone gives you 4 different choices of diamond grit. The overall length is 180mm. Each end has a 52 x 20mm section of diamond coating. Double-ended and double-sided means you have 4 options. The grades are extra coarse 120 grit, coarse 180 grit, medium 240 grit and fine 320 grit. Each end has the grit size stamped into the steel so there is no confusion. This hone is useful for sharpening or touching-up many tools such as knives or router cutters.