The place was clean and clutter-free. There are many bedrooms. I was a single person traveling and did not use all the rooms. The kitchen is small in space but very functional. It has good quality and complete set of utensils and cookwares and good for cooking. The beds are smaller by the US standards but for a single person it was good. The building is mostly quiet except sometimes during the festivals and weekends. One thing that bothered me was the neighbors smoking which I think is just pervasive in Spain.
The apartment includes pretty much everything needed to function, including washer and dryer. I had a pleasant stay. As far as location is concerned, Sestao is not a place of tourist attraction and is not the most interesting location.