This is an acoustic amplifying horn for an iPhone4 or 4s Phone in an Otterbox "Defender" series case. It helps direct the sound (thus amplifying) and increases the lower frequency response of the phone's speakers slightly. Don't expect it to sound like a Bose system but it works great in the pocket of my coat while walking.I used a support that was 17.5mm high to support the inside of the base. The rest of the horn was unsupported and printe ok as there were no sharp overhangs.This is a work in progress but is useful.