With the disclaimer that it's at least two years since I looked at mine - Pretty much so.
If you remove the top cap, it's like looking down into a can with an Allen head bolt lurking at the bottom.
Allen bolt engages existing starnut, and extender tightens down like a regular stem, and locks down like a regular stem using the pinch bolts. Top cap threads into a threaded hole center-drilled into the Allen bolt used to set the headset preload with the extender.