The battery holder holds the 4s and 5s (all we tested) 5000mah cells. It bolts in ( in two places on the one in picture, but now its 4 places). The motor mount is pretty solid, you would never hit it if you cased a jump, if you did somehow, it wouldnt hurt it. The motor has a skid under it (not shown). We can do them carbon fiber or aluminum, or sell just the transmission, just the front and rear section (so you can build your own chassis without having to make the correct bends or anything).