The H1 is a U2 transmitter strap holder. The Transmitter is fixed on the guitar strap to prevent turning or falling. Elastic band is fixed with hook-and-loop fastener tape, and firmly hold the transmitter.
Avoid some special guitar interfaces,resulting in U2 can not be inserted directly. Avoid electric guitars with preamp circuit or acoustic guitars with microphone pickup, which are disturbed by transmitters and produce high-frequency noise.
CALIFORNIA PROPOSITION 65 WARNING

WARNING: Cancer and Reproductive Harm -
www.P65Warnings.ca.gov.