The AR4 (Arrangement Recommendation 4) is our firmest arrangement latex mattress. If is designed for heavier people or people who just like a firm sleep surface. It is not hard, though. It is not like sleeping on the floor because it does have a medium firm top layer. This model is more popular than the AR1 in overall sales numbers, but as one can imagine, not as popular as the two in the middle, the AR2 and AR3. The more someone weighs the softer latex will feel. So the demand of this mattress goes up the more someone weighs. Typically people over 250 pounds like this model or if you are one who weighs less but just really like a firm sleep surface. This website will be your source for a complete mattress education so you learn what is the best mattress.