Features: Selected from metal and plastic material, firm and stable to use. This allows you to connect all types of funny thing as input. It is invention kit that makes your computer think that almost anything is a keyboards. The kit use high resistance switching to detect when you have connection even through materials that not conductive. The ATMega32u4 connection to your computer using the human interfaces device protocol which means that it can act as a keyboards or a mouse. No need to program, no need to connection lines, no need to install software, just need to connect USB to use, very simple! Specifications: Component:Metal+Plastic Size:Approx.9.4x4.8cm/3.7x1.89inch Package Includes: 1 Set Main Control Board note: 1.Please allow 1-2cm errors due to manual measurement, making sure that you not mind before order. 2.Due to the differences between different monitors, the picture may not reflect the actual of the item.