You are recommended to replace your ninja blender replacement parts every 6 months or as needed for optimal performance 2. Please check whether the gear of the bottom loosen or tighten before use. If it's loosen, please tighten it 3. Please check the rubber gasket and be sure it is put snugly into the bottom blade. (The rubber gasket is used to avoiding leakage? 4. Do not overfill to avoid spilling, do not add ingredients past the "Max" line 5. Place the replacement blade onto the cup and screw it tightly until you have a good seal 6.