5-10ml Empty Sealed Sterile Vials - 5 Pack

Several customers have indicated they are not sterile. How was this noticed?

What are the dimensions of these vials? How big is the opening, and how much does it taper in the neck?

Do they have negative pressure?

If I wanted to reuse these, is that possible? And if they are reused, how often would I need to replace the butyl stoppers (if at all?)