On 4 pistons calipers; allows a single piston to come out at the time to facilitate cleaning and lubrification.
Instructions: The brake must be fully bled. Remove the pads, present the step in front of the piston you want to come out, install the tool instead of the pads and secure with the pad pin. Pump out on the master cylinder until the piston comes in contact with the tool.
*This information is directly taken from Hope's open source tools information page
