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ADV ProductsSea to Summit Trek TKI: Big-Guy Mummy Bag That Packs Down Small

Sea to Summit Trek TKI: Big-Guy Mummy Bag That Packs Down Small

Tiny and technical, this sleeping bag can fit anywhere on your bike.

Published on 09.12.2018
For adventure riders, standard rectangular sleeping bags are just not ideal. They are typically way too big, and often too heavy making them less practical. That’s why looking to the backpacking and hiking industry for lightweight, small-packing gear is recommended for adventure bike enthusiasts who plan to camp off their bike.

Sea To Summit is a staple in the outdoor gear scene and has many sleeping bags to suit many camping situations. What I’ve been using over the past few months is their Trek TkI Sleeping Bag, which is rated a 32-degree bag.

What It Is

If you want to get crazy, there are hyper-small, hyper-light sleeping bags out there that are hyper expensive and mostly uncomfortable. The TkI is somewhere in the middle with a tapered rectangular shape that isn’t full-on claustrophobic mummy-bag-style, but isn’t as roomy as a rectangular bag. The 32-degree rating is the bag’s claimed “lower limit” zone with 41 degrees being the “comfortable” zone and 5 degrees being the “extreme” zone.

Sea to summit Tret TkI Sleeping Bag


The fill is 650 Loft Ultra-Dry Down and is what makes a warm but lightweight sleeping bag possible. Thirty grams of the duck down will expand to 650 cubic inches and it is coated with a special material making it water repellent. The shell material is 30D Nylon that is breathable yet water resistant and features a cinchable hood to keep your noggin warm when it gets really cold.

How It Works

Sea to summit Tret TkI Sleeping Bag

Zippers are important on sleeping bags and the TkI has a pretty good system. The main zipper didn’t snag when zipping it up from the inside, and the toe box has a separate zipper if you want to pop your feet out in warmer weather. Being on the wider side at 215 pounds and 5’ 8”, I still had a good amount of room to move around in the bag and didn’t feel too restricted. But if you like to spread your legs apart in your sleep, a non-mummy style bag would be a better bet. Although, wide rectangular bags typically don’t pack down as small.

The shell material looks and sounds plasticy, but it is very soft and comfortable on the skin. It also breathed really well. At no point did I feel clammy or that there was condensation in the bag.

There were some very chilly nights (one at a recorded 31 degrees) and a few times I did have to grab my riding jacket and throw it over my leg/feet area to keep from being too cold. Also, the spots where the bag was pressed against my body (shoulder and hips when on my side) those body parts were noticeably cooler than the rest of me. I would say that the 41 degree comfortable zone is probably pretty accurate and if you know that you’ll be sleeping consistantantly in colder temps, I would get a warmer rated bag or bring a sleeping bag liner to boost warmth. The Trek series is also offered in 18 degree and 12 degree rated options. Although, the penalty for the added warmth is more bulk and weight.

Sea to summit Tret TkI Sleeping Bag

Speaking of, this bag gets very, very small with the included compression sack. With the sack cinched down all the way it is about the size of a cantaloup. Just like bikes with better and better technologies each year making them lighter and smaller, the same can be said of camping gear. The huge, heavy sleeping bags of our youth have given way to much smaller, lighter, but still warm bags of today. If you’ve had your sleeping bag for a decade or so, it might be worth seeing what’s new.

Who It Is For

The TkI is for the fair weather ADV rider that values pack size and weight. Late spring, summer, and early fall is when this bag is most effective. It is also for a camper that wants more sleeping room than a traditional mummy bag, but still a hood and the option to fully unzip it to use as a blanket. I would say it is small enough for the dual-sport guy or soft-luggage guy as well, and with a liner and good, insulated sleeping pad, can stretch further into cooler climates.

Sea to summit Tret TkI Sleeping Bag

Our Verdict

This bag isn’t the cheapest that I’ve used, but it is definitely the most technical and comfortable to sleep in. The fact that a full-size sleeping bag that is nice and fluffy can compress down to the size it does is mind blowing. Every time that I would go to pack it up, I think, “How’s it going to fit?” But then once you get it in the compression bag and start working on the straps, it just gets smaller and smaller. It’s also a nice feature that it comes with a separate, much larger storage bag, since it isn’t good for the down material to be compressed for long term storage.

What We Liked

• Packs small/easy to pack down
• Soft, comfortable, breathable material
• Warm enough for moderately chilly nights

What Could Be Improved

• Perhaps thicker shell so that pressure points don’t get too cold
• The lower limit of 32 degrees might be optimistic

Sea to Summit Trek TKI Specs (Size Regular*)

SIZE: 60in x 57in x 40in
SIZE (packed): 7in x 7in
WEIGHT: 1 lb 12 oz (790 g)
FILL WEIGHT: 12.4 OZ (350 g)
TEMP RATING: 32ºF (Lower Limit)
FITS UP TO: 6 ft/183 cm
MSRP: $269
* Also available in “Regular Wide” and “Long” sizes.

Shopping Options:

Amazon Sea to Summit

Author: Sean Klinger

With his sights set on doing what he loved for a living, Sean left college with a BA in Journalism and dirt bike in his truck. After five years at a dirt-only motorcycle magazine shooting, testing, writing, editing, and a little off-road racing, he has switched gears to bigger bikes and longer adventures. He’ll probably get lost a few times but he’ll always have fun doing it. Two wheels and adventure is all he needs. 

Author: Sean Klinger

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September 20, 2018 8:05 am

Nice review, but having all the data in Imperial only makes us people of the rest of the world have no clue what you are comparing. Would be nice if ADVpulse would include metric aswell so we have an idea what you are talking about here. 🙂

Bill McStravick
Bill McStravick
September 20, 2018 9:59 am
Reply to  Dorus

typed the words right outta my keyboard

ADV Pulse
ADV Pulse
October 2, 2018 10:03 pm
Reply to  Dorus

Thanks for the feedback Dorus! You have a very good point – we will try to incorporate both units more consistently. Wish we would all just move to the metric system in the US once and for all…it’s going to happen at some point right? 🙂


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