Classic 100 Gel Flux is not exactly a gel, but a thickened liquid flux. The thickening means it doesn't splash when you apply it, and it stays where you put it. It's non-smoking, odorless and water-cleanable (as we all should be), although if you put too much flux on your workpiece you can cause the flux to smoke up. It can be used for copper foil, lead or zinc. 8 oz bottle with a flip-top lid.