Filstar media baskets have been designed with many convenience features for the user and allow for a high degree of customization. When properly placed in the filter they nest securely and all water coming into the filter will flow from the bottom up through these baskets. For best results avoid overfilling the baskets and use only media designed for the Rena Filstar XP filter system. Each basket also has handles for easy lifting from the filter during cleaning. Replace only if warped or damaged.