DescriptionTo confirm if an eggs are fertilized or not, this light will letyou see then by showing the veins. You just can't tellbefore then. You can mark your eggs with dates in pencil so that you cankeep track. This light was very helpful and was really fun to watch thegrowth of the eggs. You can check about once or twice a week to makesure that they were still growing.Features- Color: Blue, Black -Material:Aluminum Alloy, ABS - Size: 10.30X3.60X3.60cm/4.05X1.41X1.41in-Note:3 X AAA Batteries are needed.(NOT INCLUDED) -Professional and practical design with beautiful appearance, easy to carry and use. -The Egg Tester uses high-penetration and high-brightness lamp beads.-After incubator has been running for a few days, it's feasible tosee the eggs with a bright light to see inside the shells. -Whenthe lamp is lit, the hatching degree in the egg can be clearly seen, andthe hatching degree of the egg can be easily judged. -Light egg candler is a product that checks whether the egg is fertilized and grows healthy.