This is a Hi-Viz Sight known as the LiteWave H3, model KBN521.
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 1911 models with fixed rear sight; does not fit Micro.
Features:
Green tritium front with orange ring
Green rear
Sight visibility in all light conditions
Factory sight heights