I am currently using this run as an indoor cage for my two guinea pigs. I made a base myself and this is their full-time cage. My two problems are; the opening at the top is hard to access and a young guinea pig could fit through the bars. My guinea pigs never tried to escape as they feel safe in it. My guinea pigs adore this cage and have great fun doing laps of it.Giving guinea pigs this amount of space if you can is ideal. I love this cage otherwise.