Abstract: A printing system includes two image-forming units, each containing an image medium on which a powder image may be formed and an intermediate medium contactable with the image medium for transferring the powder image. Both intermediate media together form a nip for substantially simultaneously printing the powder images on two separate sides of a receiving medium. A toner is used for the formation of the powder images. The toner has a flowability, measured using an API flowability tester, of 6 or higher. A method is also provided for selecting the toner that is suitable for the printing system.