You’re in a cave, 300 feet below ground, when — suddenly — your flashlight burns out! It’s pitch black.

If you’re prepared, you have a backup light.

“Lighting is the most critical piece of equipment for caving,” says Kass Kastning, 29, an Eagle Scout and expert caver. “Always have at least three light sources with you.”

Reliable lighting is just as important for hiking and backpacking, too. So we asked Kastning to shed some light (sorry, we couldn’t resist) on what you need to consider before buying a new flashlight or headlamp.

THE LOWDOWN

Lights come in many shapes and sizes. Handheld flashlights are the most common. They are versatile because you can easily direct the light and focus it closer to the ground when hiking.

“I like smaller flashlights when I’m outdoors,” Kastning says. “They are lightweight, and you can throw them in your daypack in case you need light.”

Headlamps are like flashlights you wear on your head. Headlamps are the standard for cavers — and any other outdoorsman who need to have their hands free for climbing and handling gear. Battery-powered lanterns are used to light up larger areas for cooking and hanging around camp. Finally, signal lights are flashlights that come with several different colored lights and special blinking options that can help you call for help when necessary.

PRICE

“You can buy a cheap flashlight at a discount store, but that might not be such a good choice,” Kastning says.

You get what you pay for. Cheap lights usually are not durable and won’t last long. Expect to spend at least $10 to $15 to get a quality flashlight. Headlamps are more expensive — you can get an entry-level headlamp for about $20 to $25.

SIZE AND WEIGHT

“Big flashlights usually shine brighter, but they also weigh more,” warns Kastning.

If you mainly keep the light in your pack for emergencies or for getting around camp at night, get a smaller light. Some of the newer, more expensive small lights can pack as much power as the older big ones.

BATTERIES

Bigger flashlights require bigger, heavier batteries — and that spells more weight you’ll have to carry on the trail. That’s why Kastning likes smaller flashlights with AA batteries. In general, big batteries hold more power and last longer.

Most flashlights use alkaline batteries, but if you can afford lithium batteries, they last up to 10 years. Rechargeable batteries are another choice to consider since they are better for the environment, but they don’t hold their charge as long as other types.

BRIGHTNESS

Think about what you’ll be using your light for. If you just want a light to read by in camp, consider a small flashlight or tiny lantern with LED lights. If you need it for hiking or mountain biking, a bright headlamp with a halogen or Xenon bulb might be a better choice.

DURABILITY

“Consider getting a light that can withstand being dropped on rocks or in a stream,” Kastning says. “Ask yourself: Over a few camping trips will it be able to hold up to wear and tear?”

If the light is made of aircraft-grade aluminum or super-strong plastic, the answer is yes.

It’s also best to pick a model with a push-button switch because lights with sliding buttons can accidentally be turned on in your pack, killing the batteries or bulb — and leaving you with no light.