A 50 ft length of each ThruLine 1 mm colorway measured 7.70 grams. Internal testing also measured 90 lb straight-line breaking strength and over 60 lb knotted breaking strength. Here is why the knotted result is the more relevant strength figure for a typical knotted guyline setup.
Guyline rarely gets top billing in an ultralight shelter system. Fabric, poles, stakes, and hardware are easier to see, so cord can feel like a rounding error.
But a shelter is a system, and small pieces still have to earn their place. Once we looked closely at the line itself, the design question became simple:
How little cord weight can we carry while keeping the line useful for its intended job?
That question led to ThruLine 1 mm: a deliberately fine, two-fiber guyline for tent and tarp guylines and light-duty camp rigging.
Start with the measured number
A 50 ft / 15.24 m length of each ThruLine 1 mm colorway measured 7.70 g, or 0.27 oz.
That works out to:
- 0.154 g per foot
- 0.51 g per meter
- 3.70 g for four 6 ft guylines
- 7.39 g for 48 ft
The shorter-length figures are calculations based on the measured 50 ft length. They exclude knots, tensioners, packaging, and cutting tolerances.
This is the practical benefit: you can rig a shelter, customize each segment, or carry extra line while spending very little of the pack’s gram budget on cord.
The 1 mm diameter is the design
Moving to a fine diameter reduces the amount of material in every foot. Over a complete shelter setup, those fractions of a gram add up. The cord also coils into very little space, whether you carry a few cut lengths or the full 50 ft supply.
Thin line comes with honest tradeoffs:
- It is less glove-friendly than thicker cord.
- Tight knots can be harder to untie.
- Fine line can tangle more easily.
- Not every tensioner is designed to grip 1 mm cord.
- Small-diameter cord deserves extra care around rough or sharp edges.
ThruLine 1 mm is the gram-first option for hikers whose knots, hardware, and handling preferences suit fine line. It does not pretend that one diameter is right for everyone.
Why co-braid two fibers?
ThruLine 1 mm brings UHMWPE and high-tenacity polyester together in a co-braid. Each material was selected for a different job.
UHMWPE is the strength-focused, low-mass side of the design. At the material level, published research reports a density below water and extremely low water absorption for UHMWPE fiber. Those traits help explain why the fiber is useful when mass matters, although material data is not a substitute for testing the finished cord.
Polyester was selected for visible color and to pursue a less-slick hand than an all-UHMWPE braid. Finished-cord grip has not been quantified, so compatibility still depends on the knot or tensioning device in the complete setup.
In short:
- UHMWPE: high strength at very low mass
- High-tenacity polyester: selected for color and a less-slick hand
- Co-braid: both fiber types integrated through the finished line
See ThruLine 1 mm and the complete specifications.
Choosing the right balance
Every cord design balances weight, diameter, strength, handling, and durability.
More material can create a thicker line, but it also increases carried weight and packed volume. We designed the 1 mm version around a specific user and job: the gram-conscious backpacker building a shelter system with knots or hardware already suited to fine cord.
That is what “right-sized” means here. It does not mean that ThruLine 1 mm is right for every shelter, every condition, or every person. It means the diameter, material choices, and carried weight were considered together instead of chasing the largest possible number on a specification sheet.
Why knotted strength is the more relevant number
Internal testing measured two different results:
- Straight-line breaking strength: 90 lb
- Knotted breaking strength: over 60 lb
Straight-line breaking strength measures the cord without a strength-reducing knot interrupting the loaded section. It describes the line’s maximum result in that test configuration, but it is not how guyline is usually terminated in the field.
A knot changes how the cord carries load. The tight bends inside the knot concentrate stress and prevent all of the fibers from sharing the load as evenly. Rope manufacturers accordingly warn that knots reduce rope strength, with the amount depending on the knot, fiber, construction, and setup.
ThruLine 1 mm retained more than two-thirds of its straight-line breaking strength in our knotted test. Because most guyline setups terminate the cord with at least one knot, the over-60 lb knotted breaking strength is the more representative product-strength figure for a typical knotted setup. It tests the cord in a configuration closer to the way it is likely to be used, including the knot that will often become the limiting point.
That does not mean a knot will always fail first. A tensioner can slip or damage the line; abrasion, sharp edges, stakes, shelter tie-outs, and other hardware can also become the weakest part of the system. Different knots—or the same knot tied and dressed differently—can produce different results.
Neither 90 lb nor over 60 lb is a safe working load. Cordage safety guidance distinguishes breaking strength from a working-load limit, which depends on the application, condition, loading, and an appropriate design factor.
Most importantly, ThruLine 1 mm is not climbing equipment. It must never be used for rappelling, rescue, fall protection, human suspension, towing, or any other life-safety application.
When ThruLine 1 mm makes sense
The 1 mm version is a good fit when:
- You count shelter-system weight in individual grams.
- You are comfortable handling fine cord.
- Your knots or tensioning hardware have been tested with 1 mm line.
- Your use is limited to tent/tarp guylines and light-duty camp rigging.
- You inspect and replace cord when it shows damage.
A thicker cord may be the better choice when easy handling, cold-weather use, repeated abrasion, or a hardware maker’s stated diameter range matters more than a few grams.
The line should earn its place
Ultralight design starts by understanding what each part needs to do, then removing weight that does not help it do that job.
For ThruLine 1 mm, that meant going fine, combining two purposeful fibers, and publishing the measured results without inflating them:
Each colorway measured 7.70 g per 50 ft, with over 60 lb internally tested knotted breaking strength.
See ThruLine 1 mm and the complete specifications.
Safety note: ThruLine 1 mm is for tent and tarp guylines and light-duty camp rigging only. Straight-line and knotted breaking strengths are not working-load ratings. Inspect the cord before use, test knots and hardware at home, avoid heat and sharp edges, and never use ThruLine 1 mm for climbing, rescue, towing, fall protection, hammock or human suspension, or any life-safety purpose.
Sources: UHMWPE fiber properties and general rope, knot, and working-load guidance. These sources support general educational statements, not the finished-product test results.
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