What is the red button on a keyboard? : r/whatisthisthing

Clear plastic hollow rectangle, has a rubber tube inside of what appears to be some kind of reservoir, what looks like a rubber button, and the L shape gasket thing opens to

DualShock 4 Back Button Attachment - PlayStation 4 : Video Games

Weird plastic red key that I found in my apartment after the firefighters left after a fire : r/whatisthisthing

What are these 2 buttons for and what do they do? : r/whatisthisthing

What is this button on my keyboard? : r/whatisthisthing

What is this thing? Blue aluminum hand valve with two buttons, two gas hoses, and toggle on top. : r/whatisthisthing

New ThinkPad is a trusty favorite for business users

Black plastic angled piece with a raised cube on it. : r/whatisthisthing

R keyboard hi-res stock photography and images - Alamy