From the Super Mario Wiki
The Button tires are an unlockable tire part that first appear in Mario Kart 8. They are statistically identical to the Roller, Azure Roller, and Leaf Tires; they offer a high acceleration boost and a handling boost at the cost of mitigating speed, weight, and traction. The only difference is its appearance. The Button tires look like light brown buttons with distinctive red yarn forming an "X" in the center.
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