This is Prusa MMU2S upgraded filament buffer.

The original, shipped with MMU2S upgrade didn't really work for me. It is designed to be put in back of printer, where it doubles the size of the printer itself. Also I found it very hard to manage filaments in the buffer, and additionally, it won't fit in LACK enclosure I had. Also if you ever needed to move your printer and hat the buffer attached to your MMU, good luck.

So this is completely redesigned to address these shotcommings and more.

Fits next to the printer on its right side. Essentially it increases footprint of the printer by about 1 inch to the right, but nicely fits to LACK or any enclosure you had for your original mk3/S setup before.

Another benefit of this design is that you always see at first glance state of your filaments and it is really easy to remove filaments, push them in/out if you got MMU2 jam. The whole thing just get so much easier.

The buffer is attached to the printer frame, so when you need move printer, you need just to remove filaments and you are free as you were with i3s.

I also found this design of the buffer to work better at buffering job compare to the original setup shipped with MMU2S, which somehow didn't work for some stronger filaments, they were just pushed straight from the buffer.

It requires a bit of more from you to attach it (essentially you need to put different Z-axis holders), but I would say apart from the more plastic you need for parts thats the only disadvantage here.

It is designed so the spools can be on top of your enclosure, at bottom of it or next to printer. Just choose the orientation that suits you the best.