This badge is 7 cm in diameter (it fits just inside the palm of your hand) and can be sewed on to your backpack or jacket. It uses the same blue and yellow colors as the other Forum badges ("Camino Forum Member" badge and the "I walked the Camino Frances" badge).
Why a badge?
You do not need a badge to be a pilgrim. The idea behind this badge is for you to get in touch with other fellow forum members while on your camino. This badge is only sold on the forum store.
Also, "everyone" in Spain will know that you are a pilgrim when they see this badge. Your backpack might also tip them off :-) but the yellow shell is a known pilgrim symbol.