Smaller Cs gives a higher spatial resolution.

Philips Tecnai F20 T (Cs = 2 mm, Point resolution: 0.27 nm)

Philips Tecnai F20 ST (Cs = 1.2 mm, Point resolution: 0.24 nm)

Philips Tecnai F20 UT (Cs = 0.5 mm, Point resolution: 0.19 nm)