Each string is about 105 cm long.

Yes, SA Yo-Yo String is for all levels of play. It is good choice for starting yoyo players and it is also great for most pro yoyo tricks.

It is really simple, you just open the yoyo, take out ball bearing and switch the yo-yo strings. Sometimes you need to use pliers to take out the yo-yo ball bearing but usually  it comes out easily, so you can remove it just with your fingers.

When you play, the string wears off. It gets dirty and loses its softness. Used strings make yoyos performance worse. Old and used strings can also break.

This depends on each player. We recommend changing yoyo string every 1-2 hours of yoyo play.

There is recommended length from players waist to the ground. But you can use any length that fits you the best.

Make sure your yoyo spins strong enough to have energy to make it all the way back up to your hand. Weak throw is most common mistake. Also make sure you pull up your hand with quick and short movement, do not make long and slow pulls. Your yoyo wont probably react. Sometimes your string needs to be changed to make yoyo work well.

Always use your middle finger and attach it between second and third knuckle of the finger (you get more control). Use slipknot to attach string tightly to a finger to prevent falling it from your hand. Never use knot to connect string to a yoyo, simply untwist string at its end which will create a clean loop, put this loop around ball-bearing inside your yoyo, the loop will automatically close afterwards.

Yes, this is universal yoyo string that works with all yoyos.