Stannous fluoride concentration used in topical fluoride is:

Stannous fluoride has been used at 8% and 10% concentrations in solutions equivalent to 2 and 2.5% fluoride. Although the 10% solution is usually used for adults and 8% for children, there is no evidence of an actual clinical difference between the two. However, the most commonly used is 8% stannous fluoride preparation. Essentials of preventive and community dentistry  Soben Peter  5th edition