The Aquacomputer Multi-tool is a useful addition for setting up your watercooling setup. It includes 13, 15 and 19mm spanner widths and is suitable for Plug & Cool Connections (1/8 straight, 1/8 bent and 1/4 straight) , female hose connectors and Eheim 1048 pump connections. The tool also makes it easier to remove Plug and Cool connections, plus includes a bottle opener as well !
Check out the Aquacomputer guide here