The T4BJB16BQR is an SMT-type tactile switch manufactured by Diptronics that is 4.8 mm x 4.8 mm, with a height of 0.55 mm. The switch features a "bottom actuation" design, meaning the bottom of the switch is pressed to activate the switch. This is a single pole, single throw (SPST) momentary contact tactile switch, meaning that the contact will remain open until the bottom is pushed downwards, and will return to its open configuration when the button is released. The T4BJB16BQR offers a snap action mechanism, meaning it will open/close very quickly. The T4BJB16BQR is rated for a maximum operating voltage of 12VDC and a maximum operating current of 50mA.