Here is a quick size comparison of Sony FE 135mm f/1.8 GM lens with other related lenses: FE 24mm f/1.4 GM Lens, FE 85mm f/1.4 GM Lens, Sigma FE 135mm f/1.8 Art Lens (Approximate size).
Sony Alpha Mirrorless Cameras, Compact Cameras & Lenses Rumors
Here is a quick size comparison of Sony FE 135mm f/1.8 GM lens with other related lenses: FE 24mm f/1.4 GM Lens, FE 85mm f/1.4 GM Lens, Sigma FE 135mm f/1.8 Art Lens (Approximate size).