2pcs LTC1871 DC-DC Boost Step-up Voltage Converter Module 100W High Power Adjustable Output 3.5-35V Power Regulator Board with LED Voltage Meter

No user or operator instructions or data sheets are included. Find the download data by yourself, and please make sure you consider whether you know the operation before buying.
Size: 68x42x14mm, LTC1871 IC with External MOSFET.
Conversion Efficiency: Up to 96%. Low input voltage or a large difference between input and output voltage will degrade the current capacity and efficiency. Boost voltage to a stable regulated output. Useful for a wide range of applications, such as powering 5V USB devices from a 3.7V lithium cell, powering higher powered electronics from a 12V battery, and a wide range of automotive and electronic projects. Constant voltage regulation, not for raw LEDs. Button to switch measurement of the input or output voltage, and LED indicates the current measurement of the input or output voltage; the nixie tube can be turned off by another button. Mentioned states are able to be memorized, and are not lost even if the power is disconnected. (On-board marked "IN" LED is turned on, the nixie tube displays the input voltage value; "OUT" LED bright display is the output voltage value). Output voltage must be greater than input voltage, do not apply reverse polarity voltage, voltmeter works only when input is >= 4V