ME (and darn near everyone else)
Bo-Mar.
FWIW, check out the adjustable combat sight from MMC; awesome. Think my next 1911 (Caspian, of course) will wear these.
My Caspian 1911 wears a Bo-Mar base, now with Caspian ghost-ring blade.
Started with standard Bo-Mar rear and front blade from EGW. Then tried about a zillion front blades; ended up with the Caspian "smaller-sized" optic-fiber rod front and round-ring rear.