Some products require a foam liner to be placed inside the bottle cap. After opening the sealing, customers can use the foam liner inside the cap to reseal the product multiple times.

However, some cap designs do not have retention ring to hold the foam liner inside the cap, causing the foam liner to fall off occasionally. In such cases, an adhesive backing layer needs to be added to the back of the foam liner to firmly stick it inside the bottle cap, preventing the liner from falling off during repeated use.