Battles with Integrity

In the US, the standard business-size envelope is big enough to fit several sheets of 8.5" x 11" paper, with room to spare. It's called a Number 10 envelope. There also exists a Number 9 envelope, whose sole purpose it seems, is to be small enough to fit inside a Number 10 envelope, and yet still be big enough to hold an 8.5" x 11" piece of paper (or a check!). And the Number 11? It is intended to be big enough that you can fit your Number 10s inside.

I don't know why this amuses me, but it does.