a master cylinder having a reservoir and a cylinder formed from a single piece of molded plastic . a sight gauge is molded into a sidewall of the reservoir to permit the level of hydraulic fluid to be checked without removing the reservoir &# 39 ; s cap . a vent hole and a replenishing hole permit hydraulic fluid to flow between the reservoir and the cylinder . a baffle is provided to deflect “ geysers ” that can occur during brake bleeding when hydraulic fluid is forced up through the replenishing port . in the preferred embodiment , the baffle includes an upright portion that is used to retain a float in alignment with the sight gauge .