Along with narrow/wide chainrings, the accessory most in demand right now is the cassette convertor - removing one of the existing sprockets on your cassette and putting a large sprocket at the start. What sets the Hope option apart from the versions we have seen so far are the little protrusions just inside the arms of the sprocket (they are hard to see from this angle). The idea is that these will support the new sprocket on your existing sprockets, offering a longer like and crisper shifting.