For more precise daytime aiming, simple black sights, uncluttered by rings and colors that make the eye work harder to interpret and align all kinds of stuff, work best for me. A wide rear notch with a serrated rear face to keep it from glaring, and a single tritium vial centered low, basically invisible in day time. The front of the sight is a ledge to help with one handed slide manipulation.

The front sight is a simple serrated post with a tritium vial, again, not outlined so almost invisible in daylight. Just pure rectangle in a notch. Simple.

But in low light, you have two glowing dots, one on top of the other in a figure 8, with your point of impact right on top of that. Simple and fast.

#4096L Heinie’s S&W M&P SHIELD LEDGE Straight Eight Night Sight - Heinie Specialty Products