Self-luminous 25 Years Tritium Tube Light Keychain

Regarding brightness: This is a tritium tube, which can emit light by itself without any energy. It can emit light for about 25 years. We cannot guarantee that the brightness of each tritium tube is completely constant, because different colors and batches of tritium tubes have slightly different brightness. If you are a perfectionist, please don't buy it!
About the size:

The small is 19mm long (excluding the ring), 7.5mm in diameter, and weighs about 1.5 grams.

Medium is 25mm long (excluding rings), 7.5mm in diameter, and weighs about 1.7 grams.

Large length 36mm (excluding ring), diameter 7.5mm, weight about 2.2 grams
You can hang it anywhere you want to quickly locate in the dark, keychain, cell phone, bedside, wall, and take it with you