Shuyun Tang, founder of Original Throw, and his friends have worked with factories to make the “perfect” yo-yo strings which could handle all styles. They sent sample strings to over 100 players all over China and after 9 prototypes they believe they've created the perfect strings!
OT Slim string (22 Threads) has a tighter wind and handles regens really well. It is great for 4A play or any yo-yos with a slightly narrower gap. It is also the top choice for many 2A players!