Single Pole, Single Throw, Soft Touch Push Button Foot Switch. Normally Open.
These are good for tap tempos, feedback loops, and anywhere you want the option for a constant or fast foot tap. They're also OK for hand use as they're not too hard to push with fingers. Those looking to repair the switches on your Line 6 DL-4, this is it!
The shaft diameter is 11.77mm. I use a 12mm bit to drill a mounting hole for these.