The Cassius- Merino Athletic Tee
The performance tee that wicks like polyester — without the plastic, the smell, or the microplastic shedding.
Grown by real farmers
100% Merino
Travel Tested
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Most brands are just marketing. We are five generations.
My family has grown Merino wool since 1880 — that's a lot of seasons. We know this fibre works.
I wore my shirts for fourteen days across three countries without a single wash, so I know the fibre does the work better than any marketing can.
If it's not the best shirt you own within 30 days, send it back and I'll refund you — no questions, no forms, no fuss. But I don't think you'll need to.
— Jock Merriman, Founder.
The Fibre
Everything merino does. Nothing added.
Soft
Superfine fibres that never itch — nothing like your grandfather's wool.
Odour-resistant
Days of wear between washes. Genuinely.
Breathable
Moves moisture off your skin as vapour, not sweat.
Temperature-regulating
Cool in Tuscan heat, warm in Dublin drizzle. Same shirt.
Fast-drying
Sink-wash at 9pm, dry by morning.
Wrinkle-resistant
Hang it tonight; wear it tomorrow. No iron.
Natural & biodegradable
Grown, not made. No plastic, no microplastics shed.
UV-protective
Natural sun protection cotton can't match.
The long version lives in The Merino Field Guide.
A merino gym tee that lasts longer than the polyester one — without the plastic.
| The Cassius | Cotton Tee | Polyester Tee | |
| Wears per wash | 3–5 | 1 | 1 |
| Years of regular wear | 4–6 | 1–2 | 1 |
| Holds odour? | No | Yes | Yes (worse) |
| Hot & cold weather? | Both | Cool only | Neither |
| Microplastics per wash | None | None | 100,000+ |
| Cost per year (5 yrs) | $18 | $20 | $32 |
The performance tee that's actually clothing — not a plastic bottle.
Fabric & Construction +
Lightweight 100% superfine Australian Merino jersey. Breathable, fast-drying, and odour-resistant through repeat workouts.
Fit & Sizing +
Athletic fit, slightly tapered. True to size. View full size guide →
Care +
Wash cold on wool cycle. Lay flat to dry, never tumble. Full care guide →
The Story +
Built for movement, named in the family tradition — merino, reimagined for the gym.
The Common Questions
Order
Our sheep are shorn every 12 months. This creates the perfect length of fiber for spinning into yarn and knitted into fabrics.
Not if you take the right steps. Merino is an 'active' fiber, which means the composition can be changed by heat and friction. These can cause the scales on the fibres to interlock, causing the garment to shrink.
Yes, we ship all over the world. Shipping costs will apply, and will be added at checkout. We run discounts and promotions all year, so stay tuned for exclusive deals.
=Hands Down the Best Athletic Tee!!! As a rugby player for 30 years, I love training. I have gone through tons of shirts that get thrown away because they stink. I put this shirt through my own test of 5 dripping wet sweat training sessions. Each time I had to ring the shirt out it was so wet. Each time I would hang it up to dry. No washing. Each time I would go back to wear it and it was just as fresh as the first time I wore it. I stretched it to 7 wears. No smell. I only posted one of the pics to document the sweat. Best Athletic Tee EVER. Thanks Joc.
This is such a nice shirt
My husband loves the feel and he can workout in it and there’s no odor at all!
I randomly bought one of Sir W's other t-shirts in a pop up stand in Austin as i had heard and was curious about merino wool plus i wanted to support a small business. That tee was awesome, instantly become my favorite tee because of how comfy it was and how well it did in the Austin heat. Then i got a marketing emailed from Sir W about this new athletic tee and wow this is hands my favorite tee ever. Super lighweight, well-fitted - suits my active lifestyle and Austin heat. Plus i never have to wash the thing as it never smell lol. I never thought id be so willing to spend $90 on a tee but this is well worth it. My other tee is still perfect after two years.
I recently bought this shirt after having the George shirt for over a year. It’s a great shirt for workouts or to wear for casual social events when the weather is super hot or humid. It sounds crazy but it doesn’t smell when you sweat in it so it’s perfect for summer and workouts!
This shirt is amazing!! I bought it for my boyfriend for the gym and I swear it never smells bad! Lightweight and cute on!!