YYF Shutter YYE Edition string

Hey my friend just got his shutter yoyoexpert edition red and the string is very slipery and i really like it but it does not feel like any other yoyofactory string so i was wondering what type/brand of string they putted in it ?

If the string is inside the yoyo you have a problem.

you made me laugh but i meant on or around if you prefer and since the string (when it is rolled) is beetwen the two half of the yoyo so it is kinda in

Nobody knows ? Because i really liked it or someone knows som very slippery string that is good at most point ?