Really improves the flow especially when using model color vs model air. Vallejo recommends a 5:1 paint to flow improver ratio, but I use it in place of distilled water when mixing model color for my airbrush, so I usually mix it right around 2:1 (paint:flow improver). Smells like soapy water.

Great stuff, note the label design on mine was a little different than the images shown here, but same product.

Vallejo Airbrush Flow Improver is an essential product for airbrush painting. This product makes airbrush painting much more enjoyable because it helps to prevent needle tip/orifice clogging. This fluid acts like a lubricant for acrylic paints that may be too thick to flow properly through your Airbrush. Highly recommended for airbrush users of all skill levels.