What color is it? Sometimes that's an indication. Also, does it feel like plastic or like hard rubber? The self healing ones feel like hard rubber and are usually gray or green but I have a couple that are pink and yellow. The non healing ones are usually white or purple but I suppose they could also be other colors. The non healing ones will last quite awhile as long as you don't press too hard. Keep a sharp blade and only press hard enough to cut through the fabric. But, of course, that's with any of them even the self healing.