ARK: Survival Evolved has a lot of creatures, each with different heights. Therefore not all creatures will fit through the same type of gate. This list shows you which creatures fit through which type of gates, so you can keep that in mind when building!
This overview, and much more, is also available in the Survive ARK Companion app! Get it on Google Play or the App Store
If you come across an entry that is incorrect, please let me know so it can be updated!