Gee, I already know what my size for everything is…
But it would still be better to try the item on.
I recently ordered 6 shirts with my business name embroidered on them. The shirts weren’t there to try on so I ordered a extra large size, larger than my normal large, to make sure they would fit, even if a little bigger than I normally wore. When the shirts arrived, they were 2 sizes too small. Since they were custom embroidered, I couldn’t return them.