Here is a problem that plagues me pretty frequently. With all the product information we sort through here, dimensions can be some of the most arbitrary. Saying that something is 90mm long really doesn’t mean a damn thing to me.
Enter Sizeasy. This website allows users to input various dimensions that are then sized to scale with proportions held against other objects like playing cards, iPods, etc. So if you have a problem with spatial reasoning, you might want to give Sizeasy a looksie.