If you look at a Dagger Micro description it says specifically what optics work. It is the Shield RMSc cut so the sight has to fit that cut. I pasted the info from PSA Dagger Micro slide listing with the Holosun RDS for their slide.
Optics Mount: Shield RMSc Cut
Optic: Holosun HS407k-X2 6 MOA Reflex Sight, Black
**Available options for this footprint include:
Vortex Defender
Holosun 407k/507k
Shield RMSC