The Chitar is a lofi single 'string' guitar like instrument built using a piezo disc as a pickup and a rubber band on a hardwood base. Its output is via a 1/4" socket and it requires amplification through a high impedance device such as a guitar amp or a mic preamp.
The Chitar can be crudely tuned by loosening or tightening the band as shown in the video link below. The tone can also depend on the type of band used as shown at the end of the video.
It measures 11cm x 6cm x 2.5cm