If you've ever shopped for sports sunglasses and wondered what "Cat 3" or "Cat 4" actually means, you're not alone. Lens categories are one of the most important — and most misunderstood — specs in performance eyewear. Here's a plain-English breakdown of what each category means and which one is right for you.
What Are Lens Categories?
Lens categories (also called filter categories) are a standardised rating system that describes how much visible light a lens lets through. This is measured as Visible Light Transmission (VLT) — the percentage of light that passes through the lens to your eye.
A lower VLT = darker lens = less light reaching your eye. A higher VLT = lighter lens = more light reaching your eye.
The category system runs from 0 to 4:
Cat 0 — Clear / Fashion (80–100% VLT)
Essentially clear lenses. No meaningful sun protection. Used for indoor eyewear or night driving glasses. Not suitable for outdoor sport.
Cat 1 — Light Tint (43–80% VLT)
Very light tint. Suitable for overcast or low-light conditions only. Not recommended for bright Australian sun. Not suitable for most outdoor sport.
Cat 2 — Medium Tint (17–43% VLT)
The sweet spot for variable light conditions. Cat 2 lenses work well when you're moving between shade and sun — like trail running through bush, early morning road runs, or overcast coastal days.
Best for: Trail running, early morning/evening runs, overcast days, variable light conditions
Altra RYZE Cat 2 options:
- RYZE - Viper — Green polarised, 20% VLT. Sharpens contrast on trails.
- RYZE - Nova — Cherry pink polarised, 24% VLT. Enhances depth in bright variable light.
Cat 3 — Dark Tint (8–18% VLT)
The most popular category for Australian outdoor sport. Cat 3 handles full sun comfortably and is the go-to choice for road running, cycling, and most outdoor training in bright conditions. It's also the maximum category allowed for driving in Australia.
Best for: Road running, cycling, beach sport, most outdoor training in full sun
Altra RYZE Cat 3 options:
- RYZE - Sol — Gold polarised, 13% VLT. Reduces glare and eye fatigue on long runs.
- RYZE - Eclipse — Ice blue polarised, 17% VLT. Balanced clarity for all-day outdoor sport.
Cat 4 — Very Dark Tint (3–8% VLT)
Maximum glare and light reduction. Designed for extreme conditions — high-altitude running, snow, open water, and intense midday sun. Not suitable for driving as they reduce visibility too much in lower light.
Best for: Beach running, midday summer training, high-altitude sport, extreme glare environments
Altra S1 Cat 4 option:
- RYZE - Black Out — Blacked out lens, 6% VLT. Maximum protection for the harshest Australian conditions.
Which Category Should You Choose?
| Condition | Recommended Category | Altra Pick |
|---|---|---|
| Trail running / variable light | Cat 2 | S1 Viper |
| Early morning / evening runs | Cat 2 | S1 Nova |
| Road running / everyday training | Cat 3 | S1 Eclipse or S1 Sol |
| Beach / midday summer runs | Cat 4 | S1 Black Out |
| Extreme glare / high altitude | Cat 4 | S1 Black Out |
Does Category Affect UV Protection?
No — and this is a common misconception. Lens category describes visible light transmission, not UV protection. A Cat 2 lens can offer the same UV400 protection as a Cat 4 lens. Always check that your sunglasses are UV400 rated regardless of category. All Altra S1 sunglasses are UV400 rated across every category.
Bottom Line
For most Australian runners, a Cat 3 polarised lens is the best all-round choice. If you train in variable light or on trails, go Cat 2. If you're running at the beach or in extreme midday sun, Cat 4 is your best protection. All Altra RYZE options are $100 AUD.