I made these long and glamorous mitts to fit my skinny chicken arm, however to make them fit you, just cast on a few more stitches and then for the thumb gusset you will want to keep making increases until you have enough sts to go around YOUR thumb. I f you are confused or have questions, please send me a message here on ravelry or at lovelyarns@gmail.com and I will try to help you as best as I can.