To confirm if an egg is fertilized, this light allows you to see a dark spot and veins inside the egg. You cannot determine fertility before this stage. You can mark your eggs with dates in pencil to keep track of development. This light is helpful and allows observation of egg growth. Features - Color: silver - Material: Stainless Steel and Nylon - Size: 10.00 x 1.00 x 1.00 cm / 3.93 x 0.39 x 0.39 in - Note: powered by AAA batteries (not included) - Made from premium nylon and stainless steel material, durable for long-term use - By shining an egg candler torch through the shell, you can observe signs of development as they occur - When checking whether an egg is fresh, place the larger end of the egg upward, turn on the LED egg candler, and aim the light at the larger end - The light source is designed to not harm embryo development - Lightweight and practical egg candler for checking egg fertility and development Packing list: 1 x egg candler