It won't make your truck faster or stronger but this optional Traxxas part is very cool. It is the optional clear gear cover and besides looking cool, it allows you to see if there are rocks, dirt, etc. in your pinion/spur gears. I have sealed both ends of the driveline (heat shrink on the driveshaft, plugged the water drain holes and the foam plug for the diff hole but still dirt, sand and rocks get into the gears. Now I can take a quick look and see if I need to get in there and clean out the junk.