What is this removable tab behind my battery?

[futurejp]

Today I went to switch out my battery on my T400 and I noticed this tab hiding out under it:

http://img690.imageshack.us/img690/1545/tabx.png

The blue tab is flimsy, reminding me of those things on other gadgets that say things like "remove these tabs before using the product." Anyone know what this is for? It seems kind of odd that there may be some blockage in my computer that I haven't removed.

Thanks.

Admin Edit: Please read, and follow, the forum rules about posting in-line images!

[Harryc]

It's a SIM card holder for WWAN. Some models came WWAN ready, so even if you didn't order the WWAN card, the SIM card holder and antenna are pre-installed.