SMAKN&reg; DC/DC Converter 12V Step Down to DC 4.2V/3A Power Supply Module All epoxy sealed containers with Waterproof Housing; Non-isolated High efficiency: &gt;96%; Reliable, low heat dissipation max. 40 ; With overload / over-current / over / low voltage protection, stable performance. Light compact, convenient to use and transport; Auto recovery Widely used in Car device, such as LED Display, Hard Disk Player, MP3, DVD, GPS, etc