Park Tool BBT-5-FR11C Campy BB and Cassette Tool
The BBT-5/FR-11 installs and removes lockrings on all Campagnolo cassettes including 11-speed. It does double duty as it also removes and installs older, 12-spline cartridge bottom brackets. A must for any mechanic's tool box. It will not work on Shimano lockrings. Use by itself to install a lockring and with a chain whip to remove a lockring.