Every body is different — that's why our packs come in multiple harness styles, sizes, and hip belt options. This guide covers everything: how to measure yourself, which size to order for every pack we make, and how to dial in your fit once it arrives.
Step 1: Measure Yourself
Find Your Torso Length
Torso length — not height — determines your harness size. You'll need a flexible tape measure and a friend (2 minutes).
- Tilt your head forward and find the C7 vertebra — the prominent bone at the base of your neck.
- Have your helper place the tape at C7 and follow the natural curve of your spine.
- Place your hands on your hips and find your iliac crest — the "shelf" of your hip bones, thumbs pointing toward your spine.
- Measure down to the imaginary line between your thumbs. That's your torso length.
Find Your Hip Size
Wrap the tape around the top of your hip bones (iliac crest) — not your pants waist. The hip belt should ride on the bony shelf of your hips, where it can carry the load.
Step 2: Choose Your Harness Style
Flight Vest
Running-style vest that wraps your core with a 6-point connection. Eliminates bounce, spreads weight off your shoulders and hips, and adds big front pockets. Our most popular option — and a favorite of hikers with back pain.
Flight Shoulder
Traditional shoulder straps. Familiar if you're coming from a conventional pack, easier to slip on and off at breaks, and a better choice if a vest feels constricting across your chest.
S-Curve
Shoulder straps shaped to curve in toward the neck and out around the chest. Designed for women and anyone who wants more room through the chest.
Not sure which is right for you? Watch Shoulder Straps or Vest Harness? (3 min) or take the Backpack Quiz.
Step 3: Find Your Size — Every Pack
| Pack | Volume | Harness Options | Harness Sizes (torso) | Hip Belt | Hip Belt Sizes (hips) |
|---|---|---|---|---|---|
| Swift X | 50 L | Vest, Shoulder, S-Curve | Small 14–17″ · Large 17–22″ | Flight (removable) | S 26–29″ · M 30–35″ · L 36–50″ |
| Swift V | 49 L | Vest, Shoulder, S-Curve | Small 14–17″ · Large 17–22″ | Flight (removable) | S 26–29″ · M 30–35″ · L 36–50″ |
| Minimalist V2 | 59 L | Vest, Shoulder, S-Curve | Small 14–17″ · Large 17–22″ | Flight (removable) | S 26–29″ · M 30–35″ · L 36–50″ |
| Flight 30 Ultra | 31 L | Vest, Shoulder, S-Curve | Small 14–17″ · Large 17–22″ | Flight (optional, removable) | S 26–29″ · M 30–35″ · L 36–50″ |
| All Day Carry V2 | 35 L | Travel shoulder straps | Small 14–17″ · Large 17–22″ | Included | One size (fits most) |
| Flex PR | 50 L | Shoulder | Small 14–17″ · Large 17–22″ | Standard (removable) | XS 24–27″ · S 28–32″ · M 33–36″ · L 37–50″ |
| Flex PR+ | 75 L | Shoulder | Small 14–17″ · Large 17–22″ | Standard (removable) | XS 24–27″ · S 28–32″ · M 33–36″ · L 37–50″ |
| Wy'east Daypack | 30 L | Fixed straps | One size (fits most) | Included (removable) | One size (rear-adjusting) |
Swift X, Swift V, Minimalist V2, Flight 30, and Flex PR all feature an adjustable torso length (16–22″ range), so you can fine-tune the fit after choosing your harness size. Exactly at 17″? Broader chest — go Large; smaller frame — ask us.
Step 4: Hip Belt Details
Flight Hip Belt (Swift X, Swift V, Minimalist V2, Flight 30)
| Size | Fits Hips | Padded Length | Weight |
|---|---|---|---|
| Small | 26–29″ | 24″ / 65 cm | 6.1 oz / 173 g |
| Medium | 30–35″ | 28″ / 76 cm | 6.7 oz / 188 g |
| Large | 36–50″ | 34″ / 86 cm | 7.2 oz / 204 g |
Standard Hip Belt (Flex PR, Flex PR+)
| Size | Fits Hips | Padded Length | Weight |
|---|---|---|---|
| X-Small | 24–27″ | 22″ / 56 cm | 9 oz / 255 g |
| Small | 28–32″ | 24″ / 65 cm | 10 oz / 280 g |
| Medium | 33–36″ | 30″ / 76 cm | 11 oz / 310 g |
| Large | 37–50″ | 34″ / 86 cm | 13 oz / 370 g |
Between hip belt sizes? Choose the smaller size — you'll keep adjustment range without zeroing out the padding.
Materials: What Our Packs Are Made Of
Robic™ Nylon
High-tenacity nylon (100D–210D depending on pack) that's tougher than standard nylon at the same weight. Our best value fabric — durable, light, and trail-proven over thousands of miles.
X-Pac VX21
A 3-layer, 210-denier laminate by Dimension Polyant. Waterproof fabric with excellent abrasion resistance and a crisp, structured feel. (Pack seams aren't sealed — we recommend a pack liner for full waterproofing.)
LiteSkin LS21
A composite laminate with a clean, modern face fabric. Light and weather-resistant with a distinctive look. Available on the Swift X.
EPX200 & Ultra 200X
Premium laminates available on the ADC line. Ultra 200X is exceptionally strong for its weight — our most advanced fabric option.
Your Pack Arrived — Now Fit It (10–20 min)
Our suspension carries best when it's adjusted to your body. Take a few minutes with the guide that matches your harness:
Standard & S-Curve Harness
Flight Vest Harness
All Day Carry (ADC)
General Pack Fitting
Watch the overview video — torso, hip belt, load lifters, and sternum strap basics for any SMD pack.
Sizing FAQ
I'm right at 17″ torso. Small or Large?
Either can work — it comes down to build. Broader chest or shoulders: go Large. Slighter frame: Small usually fits better. If you're unsure, contact us with your height, torso length, and weight and we'll recommend one.
I have a petite frame. Will the Small fit me?
Often yes — the Small harness fits torsos down to 14″. But fit on petite frames varies with chest and shoulder shape, so chat with us first and we'll make sure you get the right setup the first time.
Do I measure my pants waist for the hip belt?
No — measure around the top of your hip bones (iliac crest), which is usually a couple of inches above your pants waist. That's where the belt rides and carries the load.
Can I swap harnesses or hip belts later?
Yes. On the Swift, Minimalist, Flight 30, and Flex PR lines, both the harness and hip belt are removable and available separately in our pack accessories collection.
What if the size I ordered doesn't fit?
Exchanges are easy — and we'd genuinely rather help you before you buy. Email store@sixmoondesigns.com with your height, torso length, and weight for a personal recommendation.
Still have questions about your fit?
We fit hikers for a living. Send us your height, torso length, and weight — we'll tell you exactly what to order.
Contact Us Take the Backpack Quiz