This is a well priced brake bleeding tool, similar to a Mighty-Vac used for vacuuming brake fluid through your hydraulic brake or clutch system.... Start at your farthest caliper, connect it to your bleed screw, remove the master cylinder reservoir cap and start pumping.. It will pull fluid down and out into it's cup. Keep adding fresh fluid to yoru reservoir - when what comes out is clean, stop. Go the the next caliper and repeat. This is a huge time saver when rebuild componants or replacing hoses.