Fastpitch softballs are slightly larger than baseballs all of which will be 11" or 12" in diameter. Especially if your glove is created of full-grain, instead of top-grain, leather, it will feel stiff for a little while. https://mettaray.com/questions/index.php?qa=113754&qa_1=top-pitching-gloves-every-serious-baseball-player-needs-2024