Really cool move by Muc-Off. I use their products almost exclusively to clean my bike. I haven't found any other cleaning products that are as good and as environmentally friendly as theirs.
Only thing I ding Muc-Off on is the use of aerosol cans for products like their Biio Degreaser and Bike Protect. I understand why they have to use cans but I'm leery about the propellants used.
Stupid thing is that I didn't even know their Nano Cleaner was even available as a concentrated refill. I'll definitely be purchasing refills that way going forward.