Preval comes in two parts: an aerosol power unit and a glass jar. The two pieces attach by twisting on the jar to the bottom of the aerosol unit. The Preval spray system is meant to be refillable and is small enough to be portable, whether you place it in your tool box, under the sink, or in your pocket. The Preval is the perfect pocket-size sprayer for small finishing or touch up jobs. Preval can handle all kinds of finish including paints, lacquer, shellac and gel coats. Each power unit (available separately) sprays up to 16oz. of liquid.