The phrase "to fit any size" means that something is adjustable or adaptable to all different sizes, regardless of how big or small they are.
Sentences with «to fit any size»
The cover perfectly fits the size of the passport, and extra pockets are perfect for carrying cash and credit cards. (amazon.com)
Most of the messages about school events and programs contain detailed information that would not fit the size constraints of the text messages. (snn.neric.org)
Most parents find that fitted size small diapers and one - size diapers don't fit a brand - new newborn that well. (thinking-about-cloth-diapers.com)