I know at Chatham, they are Twin XL, the same one that colleges use. But, I don't know what size they are in the other complexes. I think it also depends on the size of the rooms at the apartments. When I visited the 4 bedrooms apartments, the size of the rooms were smaller and I noticed that the mattresses seem smaller to have more space. I was in a 2 bedroom apartment and the rooms were huge, so that is why we had the Twin XL beds. I thought they were regular twin, but the sheets I brought didn't fit, so I had to buy the College size sheets and they fit perfectly. I was curious about all of this, so I went to housing to ask them and they said the bigger your room, the bigger the mattress. I also wonder why people would say the mattresses were uncomfortable, I always thought they were very comfortable and never needed a mattress pad.