This E.F.S.F Sub Flight System, also known as the Base Jabber, consists of some very large (for an HGUC) parts but don't let that fool you. There's plenty of detail to be found: 

 The Base Jabber is designed to work with a variety of 1/144 scale HG kits and even comes with foil marking stickers for extra detail.

 It is able to mount to a Bandai Action Base or can stand on its own thanks to included landing gear parts.

Pictured on the box art is the 1/144 HGUC RGM-96X Jesta Gundam which is sold separately.