  Exoplanets smaller than Neptune are numerous, but the nature of the planet
populations in the 1-4 Earth radii range remains a mystery. The complete Kepler
sample of Q1-Q17 exoplanet candidates shows a radius gap at ~ 2 Earth radii, as
reported by us in January 2017 in LPSC conference abstract #1576 (Zeng et al.
2017). A careful analysis of Kepler host stars spectroscopy by the CKS survey
allowed Fulton et al. (2017) in March 2017 to unambiguously show this radius
gap. The cause of this gap is still under discussion (Ginzburg et al. 2017;
Lehmer & Catling 2017; Owen & Wu 2017). Here we add to our original analysis
the dependence of the radius gap on host star type.
