Aquila pretty much wrote the book on ukulele strings. They feel great, they sound great, they last a good long while and once they have settled into tune, they will stay there. They will make even the cheapest uke sound as good as it ever will, and on a top end instrument they will really let the instrument sing.
The six string set comes with an extra high C and a low A, which in this instance is a wound string rather than the new Aquila red string. The wound string gives you a really nice, strident bass note to add a bit of depth to your sound, while the high C adds a bit of 'sparkle' at the top.
All in all, really great strings, wouldn't hesitate to recommend them.