Can be used as a holding or growing pen for smaller birds. This is similar to the PGB, but has NO heater. Inside dimensions are 36" long x 30" wide and 9.75" headroom. There are sliding panels on front and sides that have 1" x 4" mesh. The top half of the panels are open and the bottom half has an adjustable gate that can be adjusted outside the cage. Height can be extended with GROX expansion kit, to total height of 14".