'Modkit' assembly options include the shell with two pre-installed carbon fiber stiffening rods, scroll wheel, a ~3 gram 150mAh battery (with adhesive), and a choice of 8 dot skates. Modkits contain no internal electronics, requiring you to install your L7's internals yourself.
'Prebuilt' assembly options feature all the same, & they are completely ready to use out of the box.