I found this sock whilst repairing the central lock. Many including myself would ask, what on earth this thing is for? According to Spoon, their reservoir tank covers serve three purposes (Woww.. I couldn't figure out even one). One, they help keep the reservoir tank caps 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.
Ok.. point number 1 is quite BS to me as the factory reservoir cover is made from a very hard and durable plastic with rubber seal which could make one keep on bitching to open it once it has been tighten. So, it is almost impossible for the reservoir cover to pop out unless you banged into some walls or something. As it's capable to contain the fluid spill could make some good sense, but one still have to wonder, how much fluid this sock is able to contain since it not thick. The 3rd point seems to be clever, but then, again, it also related to the points above. If your reservoir cover is not doing it jobs properly, get it changed. Don't use this sock as an insurance because it's not. Get it for the sake of cosmetic.