This is a Hi-Viz Sight known as the Litewave, model GPLW01.
HIVIZ(R) LiteWave(R) Front Sight for Ruger GP100 revolvers. Fits models with adjustable rear sight and spring plunger retained front sight. Includes Green" Red and White replaceable LitePipes.
Features:
Interchangeable Litepipe design
Litepipe diameter .090"
