Snap-Action Switch with 15.6mm Bump Lever: 3-Pin, SPDT, 5A
 

This single-pole, double-throw (SPDT) momentary switch can be used as
a general-purpose micro switch or tactile obstacle-detector for your robot.
The switch body dimension is 20.0 x 6.4 x 10.2 mm (0.79" x 0.25" x 0.40"),
and the 15.6mm (0.61") lever arm has a semicircular bump at the tip that simulates a roller.
This three-pin switch can also be used as a two-pin single-pole, single-throw (SPST) switch that is open or closed by default,
depending on which two pins are used.