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REI Lightweight Base Layer Bottoms Review

REI Lightweight Base Layer Bottoms Review

REI’s Lightweight Base Layer Bottoms are long johns that have many uses on a backpacking trip. They can be used as sleeping clothes to keep your quilt/sleeping bag free of salt, body oils, and bug dope; as a base layer under rain pants while cooking dinner on cold evenings, or even for insect protection under shorts during black fly season. While you may be tempted to leave them out of your pack to save weight, base layer bottoms have a multitude of uses that complement the other clothing you wear or carry.

Specs at a Glance

  • Available for men and women
  • Weight: 5.9 oz (men’s L)
  • Fabric: 92% polyester/8% spandex
  • Sun protection: UPF 50

I’ve had good luck with REI’s clothing and use quite a lot of it from jackets and jerseys to hiking pants, gloves, and hats. It’s well made, true-to-size, and much less expensive than name brand products, which are probably all made in the same overseas factory anyway. I buy a lot of it on sale because I’m a frugal kind of guy when it comes to spending money.

I’ve been using REI’s Lightweight Base Layer Bottom this spring on all of my backpacking and camping trips and they’re easy to like. They’re quite lightweight (only 5.9 oz), they pack up small, and they’re easy to wash and dry without shrinking. I know many people like merino wool long underwear better than synthetics, but I typically get ten or more years of use from my synthetic baselayers vs two to three years, tops, for wool. Synthetic baselayers are nearly indestructible in my experience, which is good if you wash them very often and use them year-round.

The fabric has tiny rectangles of lighter weight fabric.
The fabric has tiny porous rectangles of lighter-weight fabric. Matching socks cost extra.

These base layer bottoms are made with polyester and 8% spandex, so they a very generous stretch. They have a wide waist band, gusseted crotch and a fly, since this is a men’s model. The fabric has a distinctive weave, with tiny porous rectangular boxes that are all over, venting excess heat and moisture so you stay dry.

I use long underwear for sleeping on backpacking and camping trips in part because it helps keep my quilt or sleeping bag clean and free of salt, body oils, and bug dope, but mainly because it helps me go to sleep. There’s something about putting on a pair of sleeping clothes (top, bottom, and clean socks) that tells my brain to downshift and make preparations for going to sleep. I’ve found these long johns to be warm and breathable for sleeping and really easy to like, especially since they are so lightweight: 5.9 oz is pretty low weight as long johns go.

REI Lightweight Base Layer Bottoms

Freedom of Movement
Fast Drying

Ultralight Long Underwear

These Lightweight Base Layer Bottoms are perfect to wear on the trail on cold days or as pajama bottoms to keep your sleeping bag clean on camping and backpacking trips.

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From what I understand, many people wear these lightweight bottoms for hiking or running in cold weather, by themselves or under a layer, but I run too hot for that. While I don’t have any experience with wearing these long johns for more active use, I imagine they’d be very good at venting water vapor through all those porous rectangular vents to keep you dry.

Priced at $40 these REI Lightweight Bottoms are a pretty good value, especially since they’re one-half to one-fourth the cost of the likes of Patagonia or Arc’teryx for not a whole lot of added value. But, they’re an even better deal if you can get them on sale.

Disclosure: REI donated these base layer bottoms for review.

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  1. I have these too. They’re also great for running.

  2. Just ordered a pair of these – 30% off sale makes them too good of a bargain to pass up.

  3. They are my ‘go to’ sleep PJs, as well as winter long underwear when it’s cold.

  4. On overnight trips my luxury is to have a fresh base layer each evening. Probably why I’ll never be a through hiker!

  5. I like the insight about wearing your base layers to bed to prevent excess oil and dirt transfer to the inside of your sleeping bag. As someone who has washed a down sleeping bag before I would recommend keeping your bag as clean as possible to avoided that labor intensive process.

  6. Do you know how these would compare to silk baselayers?

    • They’re heavier as in warmer, they’re synthetic and they’re not made with silk (which is a wood fiber like cotton).

    • Silk long u/w actually improves my sleep, but sadly fails & sweats out for active use. I’m using the Patagonia Capilene Lightweight Long Underwear Bottoms that have been discontinued (89 grams weight!) … I’ll be looking forward to getting the REI version in this review when mine are tattered. Johns under shorts are a must for me while winter hiking since I put out way too much heat.

  7. Thanks for the recommendation. I’ve worn these as my sleep and lounge in camp layer on my last several trips and they’re super comfy. Looking forward to trying them as a base layer in the cold.

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