The Drop Up base is a way to lower the height of a standard RKP truck.
No one ever wanted a baseplate sticking up on the deck side! Carver has taken the same geometry and hanger from the CV and made a baseplate that still utilizes the same lowering principle of dropping the pivot through the deck, but they replaced the mounting flange back to the bottom of the board where it belongs.
Now standard mounting hardware is once again flush with the deck, as is the base plate. Plus the smaller oval deck cut-out afforded by the streamlined base makes for a stronger deck. This is a symmetrical pair of 7.5” (10” axle width) trucks sold as a set and available in stone finished aluminum or black powder coat finish.