These are 1/2 ounce squeeze bottles with a special metal tip that screws onto the top. The tip and bottle come as a set. Extra bottles can be purchased separately. The metal tips gives a very fine line. Comes in three sizes #5, #7, #9 (thin to thick). Useful for applying gutta, water based resists and medium to thick consistency paints or thickened dyes in a fine line. If you have lost the bag the tips came in you can tell them apart by the tiny rings that run around the center of the tip. One line is a #5, two lines is a #7 and three lines is a #9.
Note: To fill the bottle, just pop out the plastic tip and then replace before use. (A funnel is helpful for filling!)
**these have a California Cancer warning on the package because the tips are brass with nickel plating, so please don't eat them or let your kids or pets eat them. There is no risk from handling them in they way they are intended, and you will probably handle them less than your pennies. Copper is on the California list too.