The price vs the output seems kind of unbalanced. Overall, I think it's less quality than GHS Fast Fret, you just don't feel lubrication on the strings. But it does offer protection and cleans the strings. I am testing a set of D'addario strings that sound, look and feel like new with this product and they are already 4 months old now, played them almost on a daily basis. On the plus side, you have a super nice system of storage for your wipe and also this thing is refillable. Basically, once the sponge is empty you can put anything there and use it as is if you don't like String Fuel. Also, this thing lasts 2x longer than FastFret (comparing by same usage for both of them)
So I am recommending it as a very useful maintenance item, just don't expect too much lubrication.