Liquid Fly-back Booster derivatives: Reusable First Stage designs, view from the top. Reusable booster is grayed out. 
Top: Zefiro 23 and H-25-based, upper stage is mount through the adapter on top of the LFBB. Bottom: H-185-based, LFBB with folded wings is attached to the side of main stage.
Own work
SkywalkerPL