We purchased the split king Reserve medium tight top after reading about it and seeing it in a mattress store. We were so excited about getting this very expensive new mattress. In less than 30 days both mattresses began to dip in the middle. My husband said he felt like he was about to roll off the bed. My back hurts so bad that I have to get up every 2-3 hours. The mattresses slides everyday and leaves a large gap in the center so we have to push it back together. The base is tied together and doesn't move. I am so disappointed. We spoke with the company where we purchased the mattress and frame and we will have to pay $250 to return the mattress. There would not be a charge if we exchanged it for another bed just like what we have but I have lost my trust in this brand. I am not sure if it would have been a better mattress if it had been a king rather than a split king. The mattress is approximately 49 days old and has been a big disappointment to us.