LEGO keychain lights use two CR2025 lithium button batteries, and the product listings indicate those batteries are included with the keychain.
Keychain lights are turned on with an on/off switch typically located in the figure’s chest. Light‑brick display models and some DUPLO sets are activated by pressing or interacting with dedicated columns, action bricks, or other built‑in buttons.
Age recommendations vary by product: DUPLO train sets target toddlers (about 2 years and up), keychain lights are typically labeled 6 years and up, and festival or display build sets are generally aimed at around 9 years and up.
Listings note general plastic for larger sets and ABS (Acrylonitrile Butadiene Styrene) for the small keychain lights and similar components.
Keychain lights commonly include a metal key ring for attachment and are sold with the required button‑cell batteries included in the packaging.
