I have not used these at this time but after looking them over and testing them with a glass of water I must say they work very well and will enable me to acurrately place drops of sugar water in the flowers. I previously used a small eye dropper which worked but always seemed to have to much sugar water in the flowers I wanted the hummingbirds to feed on. While they did find the flowers with the sugar water, they also fed on other flowers around the "treated" ones! But, the hummingbirds did come back to the flowers that I had "treated". I really do not think that the little wonders really cared wether there was a bit to much sugar water in the flowers since they stayed until they drank there fill.