No need to worry about any special gear, the operators will provide the requisite helmets, lights, gloves and knee pads. 

Kula Kai is on your way to the volcanoes and makes sense as a stop off point not only because of its location. In the cave you will gain some first hand insights into volcanic geology. 

Due to the possibility of having to crawl, it is suggested you wear long pants, sturdy shoes, and a t-shirt. These caves never get too cool so a heavier over garment won’t be necessary, in fact you’ll probably be sweating. 

The Kula Kai Caverns do offer cheaper group rates (usually over 10), so definitely give them a call or email if you think this might be the case. 

The “Maelstrom Cave”, another cave complex, offers a more extended caving experience if you’re willing to pay the extra price. Three hours will take you through two miles of caves, including lots of crawl space and the occasional goat and bat remains.