This is a set of parts designed to allow a standard 4/4 full-size violin to be electrified (so that it can be plugged into an amplifier). It includes a center-lead violin-style rod piezo pickup (part A in the labeled listing photo), a volume/tone assembly with pre-wired output jack (part D), a violin bridge (part B), volume/tone knobs (part C) and hardware (Parts E and F).
The intent is that the wooden bridge rests directly on the rod piezo, which is placed under the bridge flat on the soundboard of the violin being worked on. The lead from the piezo pickup is then plugged into the volume/tone unit, which is mounted somewhere in/on the instrument's body, as is the output jack. The adhesive plastic pad and tie strap can be used to help control the cables/wires.
Please note that how-to instructions are not included with this kit, so some willingness to dive into a self-directed DIY project is required. PLEASE NOTE: ANY ALTERATIONS YOU MAKE TO YOUR INSTRUMENT WHILE USING THIS KIT ARE YOUR OWN RESPONSIBILITY, INCLUDING DAMAGE!