Bottle contains sliding parts in it .when you shake the pen up and down the sliding parts can stir the paint in the bottle and make the paint mix well.As long as you tighten the cap of the bottle, the scratch repair pen can be kept for four years and still. New generation Car Scratch Repair Remover Pen. A must item for car lovers and drivers.it will Save lots of time and money for you to repair small scratches. Excellent design for clearing coat and auto scratch repair. permanent, water resistant.Portable. easy to use. Clean the place to be repaired, remove the iron rust, etc. ( If it is cleaned withwater, wait for it to dry before proceeding to the next step.) Shake the paint pen for 10 seconds before use to make the composition. Read Less