Needle felting foam should be firm to support the wool while you are felting. This is important for safety (felting needles are so sharp!) and also for providing a steady work surface to give you the best results with your project. Also, foam should be durable to withstand needling without falling apart on you. A felting block should last dozens of projects. This size works perfectly for all Fuzzytail Felting kit projects and is large enough for most small to medium size sculptures.