This node group produces realistic reflections at grazing angles.
It is designed for the Principled shader.
The Grazing Reflectivity parameter controls the strength. The Falloff parameter extends the reflections.
The group is compatible with 2.79 and 2.8.
Grazing reflectivity describes how reflective a surface is when viewed at low angles. Reflections become sharper on smooth surfaces.
This is also implemented in my Enhanced Fresnel group. https://www.blendswap.com/blend/23959