Review on Matrix Membrane Switch Keyboard Arduino Commercial Door Products by Carlos Massey

These are very basic keyboards that require 8 I/O pins on your controller to make 16 keys. You can find many libraries that will do all the work for you, so it's easy to incorporate them into your code if you have I/O pins. I've received these in the past with the connector bent in half for shipping and while they worked I'm glad they came with straight connectors. These three packs are a great choice, once you start using them you will want more.