Fields in light orange denote what ships, by default, with the product (if any is default at all).
Technically speaking, most sizes of cards will work in most routers, so long as they are "less than" the maximum size it can officially support. What is listed here are what the CCO Docs list and/or what is orderable. Therefore, a smaller or larger card "may" work, but likely will not be supported by TAC.
To see if a card can be interchanged between different model routers, please refer to the following URL : http://www.cisco.com/warp/public/63/pcmciamatrix.html