A: I *REALLY* wanted to to know the same thing, could not find the info anywhere readily listed, then checked the shipping info tab... "Estimated ship dimensions: 1.1 inches length x 8.6 inches width x 8.2 inches height" which lead me to the APPROXIMATE conclusion that they're about 4"tall x 3.5" wide, taking into account packaging space for the paints and the visual height to width ratio of the letters. So... maybe?
A: The Xs are 3 15/16" tall and 3 5/8" wide. The Os are 3 15/16" tall and 3 7/8" wide. I think the paint is non-toxic/acrylic based on other products by the same brand, but the packaging doesn't specify.