The most popular and typical is metal dome membrane switch. There are metal domes embedded in it and it could get perfect click feeling.
Overlay material: polyester(recommend) or polycarbonate
Oversize: <800x400mm
Colors: <13
Embossing: pillow emboss or rim emboss
Dome: stainless steel, nickel plated(recommend) or gold plated
Embedded LEDs: optional, single color, bi-color or tri-color
Embedded resistor: optional
Shielding layer: optional
Waterproof design: optional
Backlight design: optional
Connector: 2.54mm pitch female housing or 1mm pitch ZIF connector
Thickness: >= 0.6mm