Worth koa brown strings are fluro carbon strings, slightly mellower than Aquila strings and a more gentle feel to both Aquila and Hilo strings. The sets are double length, hence the higher price. The strings are very stable and don't stretch much, giving you very little tuning problems. Fluro carbon is also less sensitive to climatic changes to regular nylon strings.
This is a GCEA set for baritone, all plain strings.