This red button is 10 mm in diameter. It has two holes (be sure to put the buttonhole in going the same way as the line made by the two holes!) and can be used with either side up, depending on the look you are going for. Twelve buttons make one order. I think that is plenty for any outfit. A blouse will take 6 or 7, and the others can be used for other pieces to go in the set you make.