This is a set of optional parts for Mini 4WD car models.
From the manufacturer:
These are maroon low-friction versions of the popular slick tire, giving less grip and less bounce after landings. Fit out your whole car, or even just use a pair in various positions - there are plenty of setup options. Rear tires are thicker than front counterparts.
Compatible Cars: Mini 4WD & Mini 4WD PRO cars setup for use with large-diameter slick tires.