A piezo strip for installing under the saddle of your acoustic guitar.
These are made with lead zirconate titanate sensors under each string. These sensors emit a small electric current when they feel the string upon the saddle vibrate, thereby making the sound (which then needs to be fed into a preamp to bring it to an useable output level).
These come with a protective teflon coating around the output lead to protect the inside of the cable and the outside (your guitar). At the end is a 1/8 inch output jack (male) to plug straight into a preamp without any soldering necessary.