I’m a Chronic Overpacker. This Compression Sack Helps Me (Literally) Squeeze More Into My Luggage.

No matter the length of the trip, I’m incapable of packing just the essentials. If I can’t bring half my wardrobe, three pairs of shoes, and double the amount of underwear I’ll actually need for a long weekend, is it even worth going? So, as a chronic overpacker, I’m always on the lookout for travel gear that’ll let me cram more (and then some more) into my bags.

I’ve already invested in deceptively spacious backpacks, miracle packing cubes, and dopp kits that can fit more sundries than traditional toiletry bags. But by far, the most helpful addition to my arsenal as an overpacker has been a nylon compression bag.

Compression sacks are not just for camping

Compression sacks are essentially stuff sacks that have been modified to compress their contents. Made of nylon with a drawstring closure, compression sacks allow you to squeeze out all the air by using the attached straps to pull the two end caps together, leaving your belongings packed into a small, dense bundle.

This is great news for overzealous packers like me who love to squeeze a week’s worth of clothes into a carry-on bag that should only be able to fit, at most, enough for a long weekend. Though most compression sack devotees tend to use them only for socks, undies, and anything else that can afford to get wrinkled, I wanted to put mine to the test and see just how much it could hold, so I stuffed it with all types of clothing, from stretchy spandex to stiff denim.

For this experiment, I purchased the Sea to Summit Ultra-Sil Compression Sack. Though it’s not an official pick, the Sea to Summit Big River Dry Bag is our top-pick dry bag, so I knew the brand was reputable and trusted by Wirecutter, and the reviews for the Sea to Summit compression sack seemed positive.

Condensing all my stuff to fit was fast and simple

I used the compression sack to pack for a four-day work trip—and I felt like a modern-day Mary Poppins, defying all odds as I stuffed it to the gills, cramming in more and more until I couldn’t fit anything else. Into the bag went an entire clown car of garments, including: two pairs of pants, two pairs of leggings, a pair of jeans, two T-shirts, two turtlenecks, a long-sleeve shirt, a cardigan, and socks, bras, and underwear.

To maximize all 13 liters of the Ultra-Sil Compression Pack, I rolled my softer clothes and placed them into the bag first, layering bundles of shapeless fabric into the bottom of the bag. I laid stiffer, bulkier items, like my denim jeans and my cardigan, flat on top.

Compressing the bag and watching everything inside it shrink down to a third of its original size was like watching a magic trick. It was a fast, easy task: After tightening the drawstring opening, I was able to pull the strap and squeeze all the air from the bag in under a minute.

The resulting compressed bundle was roughly the size of a bag of flour that fit into my everyday backpack, which qualifies as a personal item on most airlines. And packing the compressed bundle of clothes into my carry-on luggage allowed me to bring even more along with me, including a portable steamer to iron out those wrinkles, my toiletry kit, and a hardcover book. Everything I needed for a long weekend fit nicely into my backpack. The slippery finish of the nylon bag meant it was easy to slide into the tight space of my pack, and when I wanted to take it out, one tug of the handle on the base pulled it free.

Your underwear is definitely a personal item

The extreme compression of the Ultra-Sil Compression Pack makes it one of the most useful pieces of gear for those traveling on airlines that don’t allow free carry-ons (looking at you, Frontier and Spirit). Personal items, which include backpacks, are permitted with even the most basic airline ticket, as long as they fit within the allotted dimensions (18 by 14 by 8 inches). Fully packed with everything I needed for my trip, my backpack easily met the requirements.

Traveling with a compression bag takes a lot of the stress out of packing for a trip, especially if you’re trying to dodge checked bag fees. But even if everything fits easily into your carry-on, or you’re checking a bag for a longer trip, a compression sack can still come in handy.

One of my coworkers brings his compression sack along on vacations to squirrel away accumulated dirty laundry, which makes unpacking at the end of his trip much easier. And the Ultra-Sil Compression Pack could end up saving the day if you need to make room in your luggage to bring home souvenirs.

Any traveler can benefit from the magical properties of a compression sack. And if you’re the type who, like me, prefers to pack for a quick weekend trip like its a weeks-long tour of Europe, you’ll never want to travel without one again.

This article was edited by Alex Aciman and Catherine Kast.