Spoon reservoir tank covers serve three purposes.
One, they keep the reservoir tanks in place during racing and spirited driving, helping prevent spillage of vital fluids.
Second, even if the caps are jarred open, the tank covers help contain the spill and minimize fluid loss.
Third, the tank covers prevent dust and debris from accumulating on the tanks and potentially contaminating the brake fluid. Furthermore, they help prevent the brake fluid from adsorbing moisture from the atmosphere, which otherwise reduces braking performance and causes corrosion of brake components.
Reservoir tank covers are sold in packs of 1 single cover (previously it were 2 but Spoon changed this).