Since the iPhone 5 uses a Nano SIM, you’ll have to trim it to fit. There are numerous tutorials out there on how to do this. I followed this one (PDF).

Some notes on cutting a SpeakOut SIM to Nano-SIM size:

• First of all, do this at your own risk. If you mess up, the SIM will be destroyed.
• I just used a scissors and cut very slowly, using the iPhone 5 SIM tray as a guide.
• If your SIM has 10 contact points (instead of the smaller newer SIMs with 6 contact points), you will have to cut into the unused contacts on SIM. Do this carefully and very slowly. Don’t cut into the embedded chip itself (see the tutorial above).
• Contrary to what others have said, the SIM thickness doesn’t matter. No need to sand it down. It fits fine.
  Here’s a photo of the different sizes of SpeakOut SIMs (click to zoom):

Unfortunately, most SpeakOut SIMs have 10 contact points on them, so you’ll have to cut through the unused ones:

Well it turns out that there’s no 3rd party unlock available for the T-Mobile Nokia 1661. I did have some success using a SIM emulator chip that I bought on eBay, though.

It doesn’t matter if you can unlock it with other tools or not, though, because T-Mobile is actually a decent mobile carrier. If you call them and ask, they’ll send you an unlock code. How easy is that? There’s even a 1-800 number to call from Canada (so you won’t use your T-mobile airtime by dialing 611 while roaming on Rogers).

You need to find your IMEI number — It should be on a label under the battery. Copy it down carefully. You can also find it by pressing *#06# on the phone.

Call T-Mobile. Tell them you’d like to SIM-unlock your phone while travelling to Canada. They’ll ask for your IMEI number and an e-mail address, and submit a request. A few hours later you’ll receive an e-mail with instructions.