What's the scale? They may be finish hydrometers and only read .980-1.020. The bulbs would be 2-3 times as big as well.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk