Ask any experienced mountaineer what the most important piece of equipment is on a climb, and chances are good they’ll say boots. If they fit properly and keep your feet warm, they are doing their job. If they don’t, painful cold feet may compromise your experience. A wide variety of mountaineering boots exist on the market today. They range from non- insulated, lightweight boots designed for short climbs with little glacier travel all the way up to heavily insulated, double boots with integrated gaiters designed for high altitude expeditions, including Everest. Most people will find that a boot somewhere in between these two extremes is ideal. But with so many options to choose from and only a vague manufacturer's description to go by, how do you know what boot is right for you? We asked the guide team over at our sister company RMI Expeditions, some of the most experienced mountain guides in the U.S. 

There's a ton of info in this post, so we've grouped it under a few sections below.

While both single (no removable liner) and double boots (outer shell with a removable liner) are well suited for a variety of mountains, they each have their advantages and disadvantages. Single boots are lighter than double boots, but they are not as warm. Double boots are easier to maintain on longer expeditions, as the liner can be removed for drying. Some models even have liner boots that can be used on their own as camp booties. Many climbers find that single boots are more comfortable due to softer materials and a more flexible upper. They do, however, have a break-in period. Double boots typically have a looser fit and may feel bulkier on your feet. They are also more rigid due to their stiffer outer shell, but require a shorter break-in period. Whether you choose single or double, make sure to test them out prior to your climb. 

“My favorite features on my boots are thermofit liners and integrated gaiter systems. The heat-molded liners make for a precise fit while the integrated gaiters have allowed me to do away with old-school gaiters. I think the most important thing when shopping for boots is to identify a manufacturer that makes a boot that fits your particular foot in terms of width. Width is as important as length for fit.”

- Seth Waterfall, Mountain Guide

• Always size up - Size up one-half to one full size for general mountaineering, single boots, and one full size for a high altitude or double plastic boot. More room increases circulation and accommodates foot swell at altitude, resulting in warmer feet. A larger boot will also allow room for an orthotic or custom foot bed, which is recommended.
• Prevent toe bang - Make sure your toes do not touch the front of the boot. Half of mountain climbing is walking downhill. Toe bang on the descent is painful. Test for this by lacing your boot up tightly and tapping your toe behind you. If your toes feel crunched against the end of the boot, size up.
• Comparative Fit - Mountaineering boots do not fit like ski boots or rock climbing shoes. These are not intended for walking in. Mountaineering boots are, so you can expect a looser, roomier fit. Tight mountaineering boots are a recipe for discomfort, decreased circulation, and potential frostbite. 
• First Impressions - First impressions are huge. Have your sock system on (almost all of our guides wear a single sock, even to the top of Everest), lace up the boots, and walk, stand, sit, tap your toes and scuffle around for 15 minutes. How do they feel?
• Brands and Models - Be aware that boot brands and models are shaped differently. If the boot fit is too tight overall, you’re likely in the wrong size. If the boot is pinching in some areas but is loose in others, you’re in the wrong brand or model.