Each Crazy Aaron's Thinking Putty® comes with its own special elements and effects that make it unique in the putty universe. We like to think of it as their putty personality. One of these elements is texture. Thinking Putty® comes in 2 (or 3 - We're looking at you Crystal Clear) firmness levels, with firm being the hardest. Best for sculpting, bouncing and building strength in your hand, firm texture putties are ideal for rough and tumble play.