General Hydroponics PH 4.01 Calibration Solution for Gardening， 8-Ounce<div style="text-align: left;"><strong>[Product Information]</strong><br><ul><li>General Hydroponics uses the highest quality electronic meter reference solutions</li><li>Growers can use our reference solutions widely among many popular brands of meters using the NaCl scale</li><li>General Hydroponics technicians check each batch to ensure that our solutions are exactly calibrated each time they are used</li></ul></div><img src="http://ecx.images-amazon.com/images/I/415DscNu5gL.jpg" noproxy><img src="http://ecx.images-amazon.com/images/I/415SkCq71hL.jpg" noproxy><img src="http://ecx.images-amazon.com/images/I/31VNubiZJML.jpg" noproxy>