a. This nail pen allows to minimize exposure of liquid formula to air so that the nail polish will last as smooth as new until the last drop.
b. Because this nail pen is All-in-one, the possibility of spilling nail polish formula is nothing so users can use it very comfortably wherever they want to use it.
c. Users can easily adjust the amount of formula according to their preference by pushing the button repeatedly.
d. The applicability of this bottle is indeed various because various tips are available.