According to a Noveske rep. they're all going on complete rifles. Once there is a surplus of lowers, they'll sell them separately. So right now, they're pretty rare.
"Throughout history, it has been the inaction of those who could have acted; the indifference of those who should have known better; the silence of the voice of justice when it mattered most; that has made it possible for evil to triumph."
-Haile Selassie I