These are good for squeezing into pub or restaurant corners, using a shelf to support an amp, mixer, or mixer/amp.
Also in home systems, to get your gear much nearer to the wall, saving much space in the room.
I got 2 of these so I could push my amps etc, much further onto my shelves.
Thomann also have similar XLR and jack plugs for the same space saving ideas.
All well worth the € to save home space, or get That gig by spueezing into a shelf cut corner in a small bar or restaurant.