Same as running shoes, but gives a greater speed boost at the cost of being more expensive to create
Each pair of running shoes gives the same base speed (default speed * 1.5). Sprinting shoes are more expensive variants that boost run speed by 300% (default speed * 3).
Different tiers are so you get armor values equal to that of the vanilla boots of the same tier.
Don't have to make the trade-off between speed vs armor.
Stacks with other methods of increasing speed (such as potions).