CDI is a subsidiary of Snap On, they actually made Snap On wrenches until Snap On bought the company so now Snap On makes CDI wrenches. the CDI wrenches are pretty much identical to Snap On except for the ratchet head which is a little larger on the CDI model. they have the same certification as well, having a current calibration and certification is mandatory in my line of business, I don't work in an auto shop. After reading the reviews I think I'm going to get them, they were all really good.
http://www.cditorque.com/