There are several types of cassettes on bikes, each needing their own special tool for removal. This one is for the screw-on 'freewheel' type which is typically found on older bikes. If you have a more modern bike then it possibly has a Shimano Hyperglide (hg) freehub type which is a different tool and additionally requires a 'chain whip' to hold the cassette still. This freewheel removal too, however, requires only something to turn it, e.g. socket set or spanner.
I decided to buy this for two reasons: it's not cheap steel plated with chrome and it's not an 'add-on' item. It's a nice quality piece of steel which is long enough to fit over the axle and fits perfectly into the splines on the cassette. It can be turned with a large hex socket, a spanner or, a 1/2 inch drivel tool (e.g. ratchet). And you need a good quality tool on a freewheel as those cassettes take a *lot* of force to remove: I ended up using a torque wrench as it had a longer handle than anything in my socket set, and was the only thing with which I could get it to loosen.
Very pleased with this for the price.