It's a sticker, and it's roughly the average size of an erect penis. So, 6x1.5"ish.
Actual size 6x1.58".
 
Don't be insecure. It's completely flat.

If you're abroad and wish to order Just This, send me an email through the Contact page and we can work out a more reasonable shipping price. I recognize it probably doesn't cost $12.50 to ship stickers internationally.