This 16-button keypad provides a useful human interface component for microcontroller projects. It's made of a thin, flexible membrane material with an adhesive backing so you can attach it to nearly anything. The keys are connected into a matrix, so you only need 8 microcontroller pins (4-columns and 4-rows) to scan through the pad.

Features:

• Ultra-thin design & adhesive backing provides easy integration to any project
• Easy communication with any microcontroller
• Maximum Rating: 24 VDC, 30 mA

• Interface: 8-pin access to 4x4 matrix

Specs:

Voltage rating: max 20V
Current rating: max 20mA
Contact resistance: 500Ω
Insulation Resistance: 100MΩ 100V
Dielectric Strength: 250VRms (50 - 60Hz 1min)
Electric Shock Jitter: < 5ms
Contact Bounce Time: 1ms
Life Span: Tactile Type ≥ one million times
Cable Length: 86mm
Connector: 8 pins (Pitch 2.54mm)
Mounted: Adherence
Operating Temperature: -40 to 80°C
Dimensions: 162 x 69 x 1mm
Weight: 6g

Reference : https://playground.arduino.cc/Code/Keypad/