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Est. 2017 · Boulder, Colorado

Tiny balls.
Big mountain energy.

Hand-painted reflective trail flags for ultrarunners who go where the maps run out. Field-tested above 9,000 ft, shipped from our Boulder workshop within 72 hours.

Shop the Flag Collection Race Director? See Custom Marking →

4.2 g · visible from 1.6 km · 612 documented ultramarathon finishes

An ultrarunner moving along a high-alpine ridge with a small reflective Weaselballs flag on their pack.
The Workshop

Built by people who have actually DNF'd.

Weaselballs Outdoor Co. was founded in 2017 by former Leadville 100 crew chief Jess Halverson and pro pacer Marco Reid. Today, seven of our craftspeople are former ultramarathon pacers with a combined 142 finishers across UTMB, Hardrock and Western States — they hand-paint every flag on the same benches where they've taped their own blisters.

We're an independent, founder-owned team of eleven. No venture capital, no Amazon storefront, no algorithm chasing — just a Boulder workshop, a Climate Neutral certification earned in 2023, and 1% of every order donated to the Access Fund through 1% for the Planet.

— Jess & Marco, plus eight very tired friends

The original 4.2 g Weaselball reflective trail flag, photographed on raw linen.
The original Weaselball · hand-painted in Boulder, CO
Flagship · 01

The Weaselball.
4.2 grams. Visible from 1.6 km.

Our flagship reflective trail flag — the lightest in its category, 38% lighter than the nearest competitor benchmarked in Q2 2024. A first in the ultralight marker category.

  • 01

    Reflective chevron pattern

    Hand-painted retroreflective ink laid down by our seven former-pacer painters; reads clean with a headlamp from 1.6 km out.

  • 02

    Ultralight carbon stem

    A 0.9 g pultruded carbon rod holds the flag at chest height without bounce, foldable to 9 cm for a vest pocket.

  • 03

    Lifetime Never-Lose-a-Flag swap

    Lost a flag on a ridgeline? We'll replace it, no questions, no receipt. 11,400+ flags honored since launch.

From $18 Shop the Flag Collection
By the numbers · since 2017

Carried to 612 finishes. Replaced 11,400 times. Shipped to 41 countries.

  1. 612 documented ultramarathon finishes carrying a Weaselballs flag, including 47 top-10 placings at UTMB and Western States since 2020.
  2. 11,400+ lifetime Never-Lose-a-Flag replacements honored — more than any competitor.
  3. 41 countries shipped to; 22% of FY 2024 revenue came from international orders.
  4. 99.2% on-time shipping across 84,300 orders fulfilled in 2024.
For Race Directors

Custom Course Marking.
Turnkey. Field-tested. Race-week ready.

Used by 38 race directors, including the founders of the Cuyamaca 100K and the Mogollon Monster 240. Three deliverables, one workshop, one shipping window.

See the full program →
  1. Custom course flags pinned along a forested singletrack trail at dawn.
    Deliverable · 01

    Course flags, printed to your spec.

    Hand-painted in our Boulder workshop to your race name, colorway and turnaround. Single-stem flags for turns, double-stem for junctions, reflective chevron for night sections. Average 6.8 g across the core line.

    • Custom colorways, your logo, your mile markers
    • Minimum order: 50 flags
    • Lead time: 10–14 working days
  2. A lightweight finish-line arch made from custom-printed flags in an alpine meadow.
    Deliverable · 02

    Finish-line arches, in a carry bag.

    3 m and 5 m aluminum-pole arches pre-printed with your race branding, packed into a single labeled duffel. Sets up in under 12 minutes with two volunteers and a mallet — no power tools, no engineering cert needed.

    • 3 m and 5 m widths, single & double-sided print
    • Includes stakes, guy lines, repair kit
    • Re-rent or buy outright
  3. Three rolls of custom fluorescent course-marking tape coiled on raw linen.
    Deliverable · 03

    Custom marker tape, color-keyed to your map.

    Reflective and non-reflective flagging tape in your chosen colorway, slit to width, wound onto labeled cores so your course crew can deploy by section. Pairs with our printed placement guide, drawn from your GPX file.

    • Up to 6 colors per order, 50 m & 100 m rolls
    • Reflective, matte, biodegradable options
    • GPX placement guide included

Ready to mark your next course? Tell us the distance, the date, and the elevation profile.

Start a Custom Marking Quote