This is a 4-string, solid u-bass made by Kala. The body is poplar and the neck is maple. The fingerboard and bridge are rosewood. It has a built-in Shadow pickup and Hipshot tuners.
The strings are black polyurethane - these take some getting used to, but the sound is amazing. A bit like a double bass.
The bass is in excellent condition and fits perfectly into a ukulele orchestra.