FlourPots~~No worries! You were right. (Great minds think alike.) The Wilton thread just has more photos from other sources.
Sal1980, welcome to the forum! There are no "dumb" questions; we are all here to help. Since you used the word "tin" instead of "pan", I'm assuming somewhere other than the USA. We typically use 2 inch high pans (not 3 inch high).
Here's a tutorial showing the use of Wilton Bake Even Strips and Wilton METAL (some are now plastic), flower nails:
If your tin is 2" high, than the collar strips need to be about 2-1/2 inch high. No science, really, except that some cake recipes rise higher than others, then reduce in size when they cool.
My sour cream white cakes tend to bake up nicely without a collar (most of the time.....), however, my chocolate cake and red velvet recipes rise about 1 inch ABOVE the rim of the pan while they are baking at 325 F. The chocolate is a stinker and shrinks back down nearly that full inch when it is completely cooled.
Look at the photos by whoknew? in the Wilton.com collaring thread mentioned above. You will see what I mean.