It's advantageously small and packs a punch with big tone, even at the lowest volumes. The ISF allows you to infinitely change the sound of your Fly 3 from British to American tones or a combination of the two, which makes this amp extremely versatile. The Fly 3 also comes with an MP3 / LINE IN jack built in, allowing you to connect to your MP3 player, mobile phone, laptop, tablet etc. and jam along to your favourite tracks; the Emulated Output jack can also be used with headphones. Capable of being battery powered, you can take the FLY 3 with you wherever you go as a set of portable speakers.