Our mixed trays are available in 9-13mm or 13-17mm and our single trays are also available in 9-17mm. You will get 3-4x strips in each tray for the mixed trays so you will get a minimum of 16+ sets per tray. The single trays have 16 strips per tray so again you will get a minimum of 16+ sets per tray, however, you will get more for your money by purchasing the single trays as you get one whole length per tray. It is much easier to keep a track of your stock with the single trays plus you will be able to see which lengths you are running out of more easily.