These parts are great for spares, or even those who want the extra diff lockers to fully lock both diffs for extra traction. The CC-01 is an offroad vehicle, so rocks and dust will eventually get into the gears, meaning that they will need replacement. As these are not common on other retailers' sites, RC Mart stocking them is a godsend! They are of premium Tamiya quality, and come with the complete set of gears, so that you can replace all gears, be it for a runner or a restoration project. The diff lockers included are also some of the best, most effective diff lockers that you can find for Tamiya diffs, short of using a racing spool. Awesome product!