There are different quality of glitter powder and many sizes for choosen. Generally in leather industry, the size of glitter are 1/24" and 1/10" are very popular.
Applied in shoes material, choose suitable loosen and thickness glitter is important.
Furthermore: the surface of glitter. In order to ensure that keep the glitter
surface smooth after gluing, it's need to make sure that the glitter powder has clear hexagon
shape without any bracing wire.