This is LM2596 DC-DC 3-40V  to 1.23-37V adjustable DC converter with current rating up to 3A peak. The voltage output is adjustable  with LED display. The module features Input reverse polarity protection,  output short protection function and Built in thermal shut down function. 

Features:

 Module Properties:  step-down module (buck)
 Input voltage: 3-40V
 Output voltage: 1.23-37 adjustable
 Output Current: Rated 2A. (Max. 3A, Please install heatsink to enhance heat dissipation.)

       if output power greater than 15W, please install heat sink
 Efficiency: Up to 92% 
 Operating Temperature: Industrial (-40°c to +85°c) (output power 10W or less) 
 Switching frequency: 150KHz

 Dimentions: 66 x 36 x12 mm