  We infer the emission positions of twin kilohertz quasi-periodic oscillations
(kHz QPOs) in neutron star low mass X-ray binaries (NS-LMXBs) based on the
Alfven wave oscillation model (AWOM). For most sources, the emission radii of
kHz QPOs cluster around a region of 16-19 km with the assumed NS radii of 15
km. Cir X-1 has the larger emission radii of 23-38 km than those of the other
sources, which may be ascribed to its large magnetosphere-disk radius or strong
NS surface magnetic field. SAX J1808.4-3658 is also a particular source with
the relative large emission radii of kHz QPOs of 20 - 23 km, which may be due
to its large inferred NS radius of 18 - 19 km. The emission radii of kHz QPOs
for all the sources are larger than the NS radii, and the possible explanations
of which are presented. The similarity of the emission radii of kHz QPOs (16-19
km) for both the low/high luminosity Atoll/Z sources is found, which indicates
that both sources share the similar magnetosphere- disk radii.
