Please be aware that these lids are for smaller bottles of a 15ml volume. They will not work on 30ml/1oz bottle necks. Confirm your bottle type is a 18/400 neck opening before ordering. For use with 15 ml/.5oz Boston Round Bottles .5oz dropper assembly with: *18/400 black PP closure *SR20 1 cc black Flouroglazed monrprene bulb *7x65mm stp Type III glass pipette. printed with .25, .50, .75 and 1.0ml calibrations.