Flashlights. The cave is lit and rangers carry flashlights.
Backpacks, large purses and tripods. These are not permitted in the cave due to low ceilings and narrow passageways. Leave them in your car or check them in at the visitor center.
Your pet. If you can, leave your pets at home. If you are traveling with your pet, bear in mind that the shade will move while you are inside the cave, and shade is limited.