These bottles are designed for both solvent and water-based paints. Their cylindrical shape is ideal for designing compact multi-gun systems since they"ll fit closer together than jar-shaped bottles. They"re available with two different cap styles:NO-RUST CAPS are solvent-proof plastic. They don"t utilize any gaskets, which means less deterioration and less parts for fewer hassles.FAST-BLAST CAPS utilize a one-piece paint passage tube, making the cap leak-proof. Their all-plastic, no-gasket construction eliminates the possibility of rust and solvent damage. The unique friction-fit joint securely holds the bottle to the airbrush.