In order to know exactly the size you need, we advise you to find your way around using the eyelets of your shoes.
Thus, 45cm will be suitable for two eyelets, 60cm for three to four eyelets, 75cm is a size that most of the time fits sneakers naturally.
These measurements are only indicative, we advise you to rely on the length of your old laces.
Green Fine Round Shoe Laces.
For more information on the use of this product you can consult the associated tutorials