Pros: Volume Boost, Some Extra Bass
Cons: Could be fragile
Stepped up to a CMOY OPAMP 2227 from my FiiO E5. Definitely a nicer volume boost, also adds some bass to my already booming HFi-580s. Fun little amp to have on the go for a good price. Haven't compared it against really high end stuff though, so can't say if it's a great audio quality booster. But for 25 - 45 bucks, they're a nice way to power cans that need it, or give a little kick to ones that don't.