CS40 Ultra Backpack

The Ideal 40L Backpack For The Ultralight Hiker

$329.97
Membership Pricing: $296.97

  • Carbon fiber frame stays & functional load lifters allow you to properly distribute your load weight
  • Ultra fabric is extra durable for long-term adventures
  • Stretch-mesh pockets for quick-stash items & easy access
Torso Size
Hip Belt Size
Description

The CS40 Ultra Backpack is built for backpackers who want maximum performance with minimal weight. At just 27 ounces, it combines a carbon fiber frame with advanced UltraWeave fabric to deliver exceptional load carrying, durability, and weather resistance—without the bulk of traditional packs. Designed for long-distance hiking and ultralight systems, it gives you the confidence to move faster and carry smarter.

Unlike typical ultralight packs, the CS40 doesn’t force you to compromise. It maintains structure and support while staying incredibly lightweight, allowing you to handle multi-day loads comfortably. Whether you’re thru-hiking or dialing in your ultralight setup, this pack is built to perform in real backcountry conditions.

Specs
  • Volume: 51L Small Torso Size (39L main, side pockets 2L each, stretch pocket 6L, hip belt pockets 1L each)
    53L Medium & Large Torso Size (41L main, side pockets 2L each, stretch pocket 6L, hip belt pockets 1L each)
  • Main Pack Fabric: Challenge UltraWeave™ 200, - UHMWPE / high-tenacity polyester woven blend, laminated with Challenge RUV™ film
  • Hip Belt Fabric: 100D Robic™ nylon diamond ripstop
  • Pack Dimensions: S Torso - 21.5" height (plus 10.5" roll top) x 10.75"width x 6.75" depth
    M/L Torso - 24" height (plus 10.5" roll top) x 10.75" width x 6.75" depth
    (scroll down for hip belt dimensions)
  • Internal Frame: 2 carbon fiber stays
  • Zippers: YKK
  • Hardware: Duraflex plastic hardware
  • Fits up to: 40" Pant Waist
  • Max Recommended Carry Weight: 35 lbs
  • Hydration Compatible: This pack can be used with most water bladders if desired
  • Warranty: Outdoor Vitals Performance Promise
Key Features

Full size, fully padded load bearing hip belt
-targeted cutouts in hip belt foam for breathability and weight reduction

Hip belt pockets with lanyard clip inside

Targeted back panel foam puts cushion where it’s most needed, and leaves voids where it’s not
-targeted cutouts for weight reduction and air movement / breathability (all for comfort)

Breathable shoulder straps with targeted cutouts and breathable ripstop mesh

Adjustable and replaceable sternum strap

Functional load lifter straps

2 carbon fiber internal frame stays

Trekking pole / ice ax retention loops

4 lashing loops on bottom panel of pack

Volumized stretch mesh pocket

Roll top closure allows additional volume

Top compression strap

3 point side compression cords

Self compressing bottom curve to keep your load higher & closer to your back

Internal hydration bladder sleeve and hydration tube port

Generously sized water bottle pockets - fit 2 bottles (smart water bottle size)

Colored white for reduction in heat on contents

What Makes The CS40 More Comfortable Than Other UL Packs?

Is The CS40 Durable Enough For Long Miles?

Simple & Efficient For Dialed Ultralight Systems

What Makes The CS40 More Comfortable Than Other UL Packs?

Many UL packs either sacrifice a frame to save weight or don't have proper load lifter structure. The CS40 uses a carbon fiber frame and functional load lifters to transfer weight off your shoulders and onto your hips.

This allows it to carry weight more comfortably than most ultralight packs—making it ideal for long-distance backpacking and thru-hikes.

What Makes The CS40 More Comfortable Than Other UL Packs?

Many UL packs either sacrifice a frame to save weight or don't have proper load lifter structure. The CS40 uses a carbon fiber frame and functional load lifters to transfer weight off your shoulders and onto your hips.

This allows it to carry weight more comfortably than most ultralight packs—making it ideal for long-distance backpacking and thru-hikes.

Is The CS40 Durable Enough For Long Miles?

The CS40 is built with some of the strongest ultralight fabrics available. It uses UltraWeave fabric, which is up to 6x more abrasion resistant and significantly stronger than traditional ultralight materials like DCF—while maintaining similar weight.

This gives you long-term durability for harsh backcountry use.

Is The CS40 Durable Enough For Long Miles?

The CS40 is built with some of the strongest ultralight fabrics available. It uses UltraWeave fabric, which is up to 6x more abrasion resistant and significantly stronger than traditional ultralight materials like DCF—while maintaining similar weight.

This gives you long-term durability for harsh backcountry use.

Simple & Efficient For Dialed Ultralight Systems

The CS40 is designed for those who prioritize weight savings without sacrificing strength or load efficiency.

The 40L capacity is optimized for ultralight gear setups, making it ideal for multi-day and thru-hiking trips when your gear is dialed in.

Simple & Efficient For Dialed Ultralight Systems

The CS40 is designed for those who prioritize weight savings without sacrificing strength or load efficiency.

The 40L capacity is optimized for ultralight gear setups, making it ideal for multi-day and thru-hiking trips when your gear is dialed in.

Key Features

Comfort Redefined

Unlike other ultralight backpacks that sacrifice comfort, the CS40 Ultra prioritizes your comfort without compromising on weight. Our thoughtful design includes a full frame, functional load lifters, targeted back panel, anatomical shoulder straps, and a wide hip belt for a comfortable fit during extended hikes.

Ultralight Innovation

We didn't cut corners; instead, we cut weight. The secret lies in the name – CS stands for Carbon Stay. We utilized ultralight Carbon Fiber frame stays, weighing only 2 oz (combined total), to efficiently distribute your load. Functional load lifters ensure weight stays off your shoulders, making every step more comfortable. And then there's the fabric...

Comfort Redefined

Unlike other ultralight backpacks that sacrifice comfort, the CS40 Ultra prioritizes your comfort without compromising on weight. Our thoughtful design includes a full frame, functional load lifters, targeted back panel, anatomical shoulder straps, and a wide hip belt for a comfortable fit during extended hikes.

Ultralight Innovation

We didn't cut corners; instead, we cut weight. The secret lies in the name – CS stands for Carbon Stay. We utilized ultralight Carbon Fiber frame stays, weighing only 2 oz (combined total), to efficiently distribute your load. Functional load lifters ensure weight stays off your shoulders, making every step more comfortable. And then there's the fabric...

Ultra-Durable Fabric

Our Ultra fabric is as light as DCF but 6 times more abrasion-resistant and twice as strong. It ensures a tough yet lightweight pack for your adventurous pursuits. When the trail gets wild, your CS40 Ultra is up to the challenge.

Streamlined Design

Embrace simplicity with a minimalistic yet feature-rich design. We kept the essential features you need while eliminating unnecessary bulk. Functional load lifters, stretch mesh pockets, and ample space in the main chamber make this backpack a reliable companion.

angled front view of CS40 Ultra backpack with a focus on large stretch mesh pocket

Ultra-Durable Fabric

Our Ultra fabric is as light as DCF but 6 times more abrasion-resistant and twice as strong. It ensures a tough yet lightweight pack for your adventurous pursuits. When the trail gets wild, your CS40 Ultra is up to the challenge.

Streamlined Design

Embrace simplicity with a minimalistic yet feature-rich design. We kept the essential features you need while eliminating unnecessary bulk. Functional load lifters, stretch mesh pockets, and ample space in the main chamber make this backpack a reliable companion.

Ideal For

  • ultralight backpacking
  • thru hiking
  • long-distance efficiency
  • ultralight load carry comfort
OV Media Mentions

Design Story

Frequently Asked Questions

Product, Shipping, & Warranty Info

Full Description

2 Ounces. The difference between being comfortable and not.

We’ve known experienced thru-hikers that avoid some amazing remote backcountry because “the weight required for the long carries would be too uncomfortable with their frameless packs.”

So we asked ourselves, "What if we could design a frame that weighs as much as a sip of water, but could still carry all the necessary gear and weight comfortably, no matter the distance or season?"

That’s exactly what the CS40 Ultra is - the ideal 40L ultralight pack for the ultralight hiker!

It’s comfortable, durable, & stable - even if you are hiking a lot of miles all day!

And this thing is LIGHT.

There are a lot of ultralight backpacks out there that are so minimal that they aren’t even comfortable. But the CS40 Ultra was designed for extra comfort even while maintaining an ultralight weight. 

  • Comfort Redefined: Unlike other ultralight backpacks that sacrifice comfort, the CS40 Ultra prioritizes your comfort without compromising on weight. Our thoughtful design includes a full frame, functional load lifters, targeted back panel, anatomical shoulder straps, and a wide hip belt for a comfortable fit during extended hikes.
  • Ultralight Innovation: We didn't cut corners; instead, we cut weight. The secret lies in the name – CS stands for Carbon Stay. We utilized ultralight Carbon Fiber frame stays, weighing only 2 oz (combined total), to efficiently distribute your load. Functional load lifters ensure weight stays off your shoulders, making every step more comfortable. And then there's the fabric...
  • Ultra-Durable Fabric: Our Ultra fabric is as light as DCF but 6 times more abrasion-resistant and twice as strong. It ensures a tough yet lightweight pack for your adventurous pursuits. When the trail gets wild, your CS40 Ultra is up to the challenge.
  • Streamlined Design: Embrace simplicity with a minimalistic yet feature-rich design. We kept the essential features you need while eliminating unnecessary bulk. Functional load lifters, stretch mesh pockets, and ample space in the main chamber make this backpack a reliable companion.

Lightweight, durable, & streamlined  – the CS40 Ultra is the ultralight solution for hiking without sacrificing comfort. We kept all the best features you need, and got rid of the ones you don’t! 

Product Care

Spray off both the outside and inside of your backpack frequently. 

To further prevent wear and tear, try to keep your backpack out of the dirt by hanging your backpack up where possible. 

If you really feel the need to get soap involved, get a tote or fill up your tub with water, and put just a little bit of that NikWax Tech Wash we mentioned before in there.

Soak your backpack in that mixture, scrub it a little bit, and the make sure it gets completely rinsed off. 

Once again, spraying off and cleaning your backpack is something that should be done frequently!

How long does shipping take?

Orders for in-stock items will begin processing 1-2 days after your online purchase is completed. Please note that business days are Monday through Friday, excluding holidays in the United States. Once processed, Priority shipping generally takes 1-3 days to arrive. Note that USPS Priority shipping is a time estimate and not guaranteed. You will receive an email notification once your package leaves our warehouse.

If you place an order that includes a backordered or pre-sale item, we will hold the entire order until the pre-sale item is in stock. If you would like to receive the in-stock items sooner and split your order into two shipments, please place two separate orders or pay an additional shipping fee to have the order divided into two shipments.

Do you ship to addresses outside the US?

Some countries may be excluded from our shipping options due to extremely high shipping costs, unsafe conditions for US carriers, or unreliable delivery services. To check if we can ship to your country, please go to the Checkout page and enter your shipping address.

Customers have the option to prepay duties and taxes for certain countries. If these fees are not prepaid, customers may be responsible for them upon delivery, depending on the import laws and regulations of their respective countries. We recommend checking with your local customs office to see if these apply in your area. APC Economy Shipping

Please note that the situation regarding duties and taxes is constantly changing. We are working to stay updated on the varying shipping costs as they evolve. Also, Live Ultralight Members and Peak tier members do no get free shipping to international addresses.

What is your returns/exchange policy?

Shop with Confidence: OV's Simple Returns Policy

  • Free First Exchange:* Enjoy your first exchange at no extra cost with each order (USA only).
  • 60-Day Return Window:** You have 60 days to return items; this is extended to 90 days for purchases made in November and December.
  • Easy Return Shipping:* We provide return labels or QR codes for your convenience (USA & Canada only). 

For more information, please visit our Warranty/Returns page. 

https://outdoor-vitals.loopreturns.com/#/

*Please note: Clearance items are final sales and are not eligible for returns or exchanges. Items such as soft flasks (included with our Skyline Fastpack) cannot be returned due to sanitary reasons. If you choose to return your fastpack, a $15 charge per bottle or flask will be deducted from your refund, unless the bottles or flasks are returned with their original packaging still intact.

Do you have a product warranty?

Our gear is made with the goal in mind of balancing ultralight weight, performance, comfort and durability. We believe in the “Live Ultralight” mantra so we focus on ultralight weight and performance while maintaining durability thresholds established for each product.

Our warranty covers manufacturing & workmanship defects for the Expected Lifespan of our products. Expected Product Lifespan is determined by OV Gear Specialists using the following criteria:

  • Product design intent & materials specifications
  • Intended use of the product
  • The specific issue encountered with the product
  • The age of the product (based on Manufacture date)
  • Brand Story

    From humble beginnings to now - find out what makes us who we are & how we are contributing to the outdoors.

  • Design Philosophy

    We don't just go for the lightest design. Find out what makes OV different & what "Performance-First" actually means.

  • Live Ultralight Membership

    Essentially a free savings account for gear that gives you year round discounts...