Nickel-plated screw metal caps are preglued well for you,and they are very easy to use. 

As you can see, we have already preglued the metal caps to the glass vials for you ... and you can screw off the stoppers very easily and fill it yourself . The hole is about 2.3-2.5MM ,so you only can put very small items,such as rice, sand, very mini flower or perfume,essential oil inside...