\usepackage[paperwidth=185mm, paperheight=255mm, hmargin=3cm, vmargin=3cm]{geometry}
\usepackage{geometry} \geometry{paperwidth=185mm, paperheight=255mm, hmargin=3cm, vmargin=3cm}
\usepackage{fapapersize} \usefapapersize{*,*,25mm,*,30mm,*}