the cylinder is a "push" stick. it pushes the bottom of the airless pump back down so you can refill it.
answered 1 year, 8 months ago
If you mean the skinny one that looks like a clear straw, it is to fill the pump with your product of choice such as liquid foundation, shampoo, etc. - it requires the tube as the 'airless' pump doesn't just open and you pour in the product...
Hard to explain, but it is for filling the pump bottle.
Hope that helps!
answered 1 year, 9 months ago