Material: Usually the same plastic as the tube (PP) to ensure a consistent look and feel.
Function:
Protection: The primary job is to seal the product, preventing it from drying out, collecting dust, and protecting it from damage during transport. It also contains the scent.
Hygiene: It prevents foreign materials from contaminating the product.
Closure: Lids typically click or snap onto the top of the tube. A good, tight seal is crucial for product preservation.