The Big, Little, and Tall Dippers are designed to hold wet, messy foods like yogurt, applesauce and dips. They contain a food-grade silicone rubber seal in the lid to prevent leaking. When the Dippers are placed inside your PlanetBox the lid of the PlanetBox will seal the Dippers when the latched is closed. If you want to use the Dippers separately for snacks, you should either pack dry food in them or place a rubber band around them to engage the seal. The Dippers will fit in the outside pocket of the PlanetBox Carry Bag (both Launch and Rover) for easy access during snack time. The silicone material used for the seal is a fully cured, synthetic rubber that is inert and stable at high temperatures. The silicone material is tested and certified to be free of lead, cadmium, mercury and a host of other toxic materials. The seals in the dippers are designed to pop in and out – in order to ensure proper and thorough cleaning. We prefer this approach over attaching the seals with an adhesive as food could eventually get stuck under the seal and become difficult to properly clean. You can remove them when cleaning, and put them back into place once they are clean and dry. If you lose a seal you can order a replacement through our website.