The box set also includes other stuff. There is more live stuff and finally a release of the very rare single Tears Began To Fall/Junier Mintz Boogie.
Along the CD box there is a release of two three LP sets. One of them includes a remastered release of the Fillmore East, June 1971 album. The other has the Rainbow Theatre, London concert of December 10, 1971 where Zappa unfortunately was severly injured when being pushed off the stage by a member of the audience.
Lots of more information here:
https://www.zappa.com/news/zappas-legendary-1971-fillmore-east-run-and-shocking-final-rainbow-theatre-gig-commemorated