SuperCool Slide Rule by SuperCool Slide Rule<div style="text-align: left;"><strong>[Product Information]</strong><br><ul><li>#1 Training tool used by Colleges， Universities and Training Centers</li><li>SuperHeat &amp; SubCooling charging of both R410a and R22</li><li>Duct Calculator that calculates CFM of Metal and Flex Duct</li><li>Access to approximately 100 free tutorials by scanning the QR code on the tool</li><li>Pressure Drop and Sizing for - Rectangular Metal， Round Metal， AND Round Vinyl Flex</li></ul></div><img src="http://ecx.images-amazon.com/images/I/51C3qgcUbXL.jpg" noproxy><img src="http://ecx.images-amazon.com/images/I/51EtFcGPZQL.jpg" noproxy><img src="http://ecx.images-amazon.com/images/I/51NtR3Hct3L.jpg" noproxy>