Coke Bottle Effect
When a woman's vagina is tighter around it's opening and super loose in the inside. Similar to how a 2L coke bottle entrance is shaped. It provides a really strange feeling.
Stick your finger in a 2L coke bottle and wiggle it around.
That way you can get the full meaning of Coke Bottle Effect.
That way you can get the full meaning of Coke Bottle Effect.