It is on the ball of my foot about 1 1/2 inches below my second smallest toe. It is about 1/2 cm in diameter not totally round but close to it. It is raised a little so you do feel there is something there when you run your fingures along that spot. If I pull the skin tight it almost looks like fluid inside or white. But it is not a surface blister - can you have a deep blister? It is not red or warm.
Hope this helps.