Highlining gear has evolved fast. What follows isn't a complete rigging course — that's what experienced mentors are for. It's a look at some of the more interesting technical decisions in the gear stack, specifically the stuff that isn't obvious until someone explains it to you.

The Webbing Problem on Long Lines

For a long time, 25mm webbing was standard. Then the big-line community ran into a consistent problem: on lines over 300 meters, wind catches the flat surface and causes the main and backup lines to oscillate and collide. The fix was going narrower — 20mm webbing cuts wind surface area by about 20%, which sounds modest until you're on a 500-meter line in a cross-breeze and the difference between a walkable line and an uncontrollable whip becomes very real.

That width shift forced a rethink of compatible hardware too — weblocks, shackles, and line grips all need to be sized or adapted for 20mm. It's not plug-and-play from 25mm.

The Sandwich System

For lines that push past 200 meters, a lot of big-line riggers use what's become known as the sandwich configuration: different webbing for different sections of the same line.

Spider Silk MK5 (Vectran fiber, 40 kN MBS, 40g/m) goes at both ends — roughly 50–100 meters on the static side and 100 meters on the tensioning side. It's grippy, hardware-compatible, and handles the constant contact with weblocks and shackles well. Silk 99 (Dyneema SK99, 40 kN MBS, 19g/m) makes up the bulk of the middle section. At 19 grams per meter it's absurdly light, barely stretches (around 1.8% at 6 kN), and has essentially no creep — meaning the line holds its measurement across multi-day projects.

The weight math actually matters. On a 600-meter line, switching the middle section to Silk 99 versus using Spider Silk throughout saves roughly 12–15 kilograms of webbing. When you're hiking to a remote alpine anchor, that's a meaningful number.

Why Silk 99 Can't Touch Hardware

This is the part that catches people off guard. Silk 99 is made from Dyneema SK99, which prioritizes molecular-level strength and minimal weight over surface friction. The consequence: it will slip in a weblock when single-wrapped. Double-wrapped, it starts bending the front pin around 24 kN. It's incompatible with line-locker rings entirely.

This isn't a defect — it's a deliberate tradeoff. Spider Silk MK5's Vectran construction trades some weight for the gripability that hardware requires. This is why the sandwich configuration exists: Silk 99 where you need featherweight strength in the middle, Spider Silk where hardware contact is inevitable at the ends.

Hardware Worth Knowing

Weblocks: The seaHorse (Slacktivity) and Alpine WebLock 6.1 (Balance Community) are the two that dominate. Both work with 20mm and 25mm (with spacers), maintain 95%+ webbing strength through a spiral diverter design, and have working loads around 10–12 kN.

Shackles: Van Beest bow shackles (1/2" or 12mm) are the industry standard for primary connections. The KingPin aluminum shackle (48 kN MBS, 107g) is worth knowing about for weight-conscious rigs — EN362 certified and noticeably lighter than steel.

Soft shackles: 12-strand Dyneema rope shackles weigh a fraction of steel equivalents at comparable strength (around 40 kN for 6mm versions). Essential for alpine rigs. Inspect religiously for abrasion — a degraded soft shackle can fail well below its rated load.

MightyLocks: For backup anchors specifically, MightyLocks retain 85–90% of webbing strength compared to traditional line-locker methods that cut strength by 25–30%. Around $30 each. Worth it.

Grog Splices

A grog splice is a locked loop termination in Dyneema or similar cord — used at anchor connection points as an alternative to metal shackles. Done correctly, a grog splice retains close to 100% of the cord's rated strength. It's also lighter and more packable than hardware. The technique is finicky to learn from a description alone; it's the kind of thing you want to see done in person and practice before trusting on a real rig.

Where to Buy

Balance Community (Colorado) manufactures much of their webbing domestically and sets the documentation standard — transparent MBS data, published test results, clear working load specs. Slacktivity (Switzerland) pioneered ISA certification standards and makes the seaHorse system. Spider Slacklines (Italy) and Slack Inov (France) are the main European alternatives with competitive pricing. Don't buy gear without published test results and clear MBS ratings.

For the bigger picture on long-line logistics and rigging, the long highlines overview covers getting lines across gaps, anchor forces, and the WLL math. And if you're just getting into the sport, the community piece is probably the right starting point.