Icon - ICNS Format.

256 x 256
 icon 256x256Download
128 x 128
 icon 128x128Download
64 x 64
 icon 64x64Download
48 x 48
 icon 48x48Download

32 x 32
 icon 32x32Download
16 x 16
 icon 16x16Download

More icons from the Social Twitter Chrome icon set: