This is a Ceramic Hone that comes with a wooden handle, has a 1/2 inch diameter and is 10 inches long.
Ceramic Hones/Steels are better than metal or even diamond steels. Both metal and diamond hones are known to be very aggressive and leave micro grooves and burs on the blades edges. Ceramic is smooth by nature and doesn't leave such. Instead it polished the edge and removes any burs.
The purpose of hones is quite simply to allow you to quickly maintain an edge without having to pull out and setup the entire sharpening kit. You shouldn't rely on this completely for sharpening, but having it about for a quick repair & touch up is handy.
This one is ideal for a knife that hasn't been maintained as it should have been using the Fine steel (1200 grit). Or if you have a chipped or rolled edge. Use this one first, then follow up with the Fine steel for a complete polished edge.
Not all ceramic steels are the same. Cheaper ones may be less dense or clog quickly, requiring more frequent cleaning. These steels are tried and tested and built in the USA.
