As stated above, HC and EC are water based products. I called Hi-Temp yesterday to clear up several things. Hi-Temp Light Cut and Medium Cut are solvent based products. Heavy Cut and Exreme Cut are water based products. What does all this mean? The solvents in LC and MC soften the paint and allow the abrasives to work. This allows you to operate the rotary at lower speeds 1200-1500. The solvents also allow the LC and MC to work better with an orbital because the solvents soften the paint. According to Hi-Temp, Heavy Cut and Extreme Cut need to be operated at higher RPM's with the rotary because there is no solvents to soften the paint. HC and EC need the heat generated by a high speed rotary to work properly. They said HC and EC will not work well via an orbital because there is not enough heat generated by an orbital. The products will hide scratches and swirls but not remove them. Again this is according to Hi-Temp. In my experience the HC and EC wil correct defects via orbital. They said the LC and MC are better choices for orbital use. Again, this all comes directly from a knowlegable representative at HI-TEMP.