Roughly 2" inches wide and about 3/8" thick.
There's about 15-20 per package
The shims in the pack I bought were 15 inches long, 1-1/32" to 1-1/16" wide, and tapered from 1/4" at the thick end to less than 1/16" at the thin end.
At my local store in Birmingham, Alabama, these shims don't appear to be northern white cedar. The packaging says made in Canada but does not say anything about what kind of wood it is. There is no aromatic cedar smell at all, but then I don't know if northern white cedar is supposed to be aromatic like the eastern red cedar we have in the south. These are Irving brand like the ones shown on-line, but the wood is whiter than in the on-line picture and the bundles are wrapped in plastic rather than being strapped.
They do not state they are treated, and appear natural. They are cedar which is rot resistant, however, do not expect them to last outdoors.
There are 45 shims in the pack I received in SoCal.
There were 42 shims in the pack I bought.
These shims can be used to install doors or windows, e.g. shim out the frame to have it plumb and level.