These sights are visible in zero light conditions! The sights have built-in tritium capsule developed by Swiss Microtech.
The capsule is filled with tritium gas that is self-luminous and will glow for 25 years.
Tokyo Marui Hicapa 5.1 Gas Blowback
★ ★ ☆ ☆ ☆
CAPA5.1 match the Hi-custom not supported.