You saved me! I inherited a bunch of Hakko heads without the base unit. Got an FM-202 on Ebay but forgot about the card. At first I thought it didn't work, but I used yellow filament, and apparently the light inside the unit can pass through the yellow. Used silver and it works beautifully! Thank you thank you!

Yes, it is 1x1 inch. The real one sticks out of the machine more, and is longer, but I didn't see the need for that.

Is it really only 1 in by 1 in?