Has someone exprience with adding gimp-brushes

Has someone exprience with adding gimp-brushes

rubberduck's picture

i want to convert something from me (http://opengameart.org/content/details-for-metal-texture-creation-sets)

 into gimp-brushes and i have a problem there. i have a loss of quality and they are smaller too.

what can i do?

do you know, why this happens and how can i make this right??