That brush looks cool but I can see 2 things that won't work for me already.
1.I really don't care for dual ended brushes lol. They're difficult to store and even if they're laying down, I don't want the ends to pick up something from where it's rolling around.
2.Sponges eventually go bad. They're not meant to last forever and once this sponge goes bad you then only have one good end.