Not neccesarily - often sims are delivered as a sort of "russian doll" - you get the ancient "credit card" with a mini-sim you can break out, with a micro-sim inside that you can snap out again.

I'm using a (formerly) micro sim in my n900, it just snapped back in to the plastic ring left when I broke it out of the mini-sim to use it in my N9 for a while.

(hope this incoherent ramble is understandable)