This is a Hi-Viz Sight known as the LiteWave H3, model GLN321.
HIVIZ(R) LiteWave H3 sight combines Tritium with our LitePipes technology for day/night performance with 24 hour illumination. Front and rear sight are green. 12 year Tritium warranty. Fits Glock models 42 and 43
Features:
Green tritium front with white ring
Green rear
Sight visibility in all light conditions
Factory sight heights