A tool to add 0.2mm thickness o-rings onto Cherry MX style keycaps. It helps you quickly press the o-ring onto the keycap. The recess in the top of the tool is tight enough to pickup o-rings so you don't have to start them on the stem before using the tool.

The short three post keycaps have the outside posts too close to the end for this tool: R4 1x2 (backspace), R1 1x2 (numpad zero), numpad plus and numpad enter.