Fluid ReservoirThis reservoir is meant for holding hydraulic pump fluid.How to Use: Periodically, check the fluid level in HPU With the trim tabs completely retracted, the fluid level should be about 2" from the bottom of the reservoir (approximately 22 ounces) refill, remove the Lexan cover and filler plug located at the front left-hand corner of the reservoir Fill with any type of automatic transmission fluid (ATF) only Brands running HPU with excess or a lack of fluid will not cause damage to the trim tab system This product may not be returned to the original point of purchase. Please contact the manufacturer directly with any issues or concerns.