We used this for our dog when she was younger and it was great for keeping her out of unwanted areas.
Note: the green string is only there to keep the gate closed whilst it was stored. When it's installed it's not necessary. There is a catch which means that the gate can open both ways.
Dimensions:
30 " tall
28" wide
2" gap between bars
The gate is adjustable to fit multiple door width. the extension is 3.5" wide and the bolts are 3.5" long so could accomodate a gap of up to 38.5" theoretically.