15" 4 stud Mondeo/Focus Steel Wheels

[Bonzo]

I find some of the online wheel fitting guides useful.

Quite a good one at Alloy wheels . com
All you need to do is enter the make,model & size

They have some tasty alloys too

Once you find out the source car for the steel wheels, compare the sizes with the sierra wheels.
Every chance that they are the same.

When you said spare wheels, I had visions of a Roadster fitted with a set of Space Savers
No idea why that popped into my head