For Curt's main Ko'olau CS Tenors (2009, 2017), which there are two of and both are C Tuning with a Low G. Thomastik-Infeld—Classic-N Strings—These are the custom set of strings that I use for both of my Ko'olau CS Tenor ukuleles and come from two different Thomastik-Infeld classical guitar sets. They are also available through our family Funky Frets Music Store and right here on LearningUkulele.com.
The flatwound string four and three last a long, long time compared to wound-round strings. There is a nice balance across the entire set. I (Curt) never used a wound string three until this set.
NOTE: This string set WILL work on a Baritone Ukulele and G Tuning (D G B E).
A Dedicated Ukulele Strings Section
For more information on a lot of ukulele string brands check out the Learning Ukulele with Curt dedicated Ukulele Strings Page
for links, information, brands, types of string material, changing strings, and string miscellaneous string resources.