Latest Thinking on Capilene 1 and 2 / Merino

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I agree with Rick. However, if you're talking about a lighter weight top that you'd take INSTEAD of your Cap 4 hoody, I prefer Capilene 2. It comes in a zip-neck, so venting works better. Also, it's quicker drying and lighter weight than Cap 1.

However, Cap 1 does has some utility, as it feels cooler on the skin in really hot weather. You feel more 'flash-off' with Cap 1. I found the stretch Cap 1 to provide the strongest cooling effect – probably because it's closer to your skin. It felt similar to Coolmax fabrics, to me.

That said, for the ultimate in lightweight fabrics, Outdoor Research's Echo L/S zip tee is the best, right up there with Arc'Teryx Phase SL – but the looser fit of the OR garment works better, IMO.

If you don't need the stench resistent properties of Merino, I'd avoid it. It's not very durable at all, retains more water, takes longer to dry, etc.

I agree with Brian. The Phase SL fabric is amazing. If you want a looser fit I the "Motus" shirts by Arcteryx use the phase fabrics but have a shirt like fit instead of baselayer (meant for running/aerobic activities).

I haven't tried the Echo Tee by OR but may need to now. I love my phase Sl longsleeve probably more than any other piece of gear that I own but competition is always a good thing (and OR is usually on sale with Arc is not).

Thanks guys. I'm looking for a piece to wear when the weather is too warm for the Cap 4 (not as a layer under the Cap 4), which I've worn to 70 degrees.

The stretch cap 1 is heavier than the regular cap 1 but I do like the UPF protection. I may pick it up and add the Cap 2 zip neck and see which one I like better across different conditions.

Based on my last thread on UPF ratings, I may also look into purchasing a button down as another warm weather hiking option.

I've found the button downs pretty unbreathable – just something to watch out for.

Try as I might button down shirts never suit me for hiking in hot weather. They hold moisture under my shoulders and back which leads to chafing. My fishing and the like, such issues matter less.

Stink factor aside, I really like the new Cap 1 stretch for hot weather hiking. Even though the fabric is heavier it feels cooler than Cap 2, and the soft and relatively substantial feel is chafe proof.

The newer merino/poly blends are worth looking at. 20-35% poly seems to be the range which preserves wools benefits while giving it some more durability. I still find pure synthetics more durable and faster drying.

"right up there with Arc'Teryx Phase SL "

And its little brother, the Motus, which is by far the best late spring-early fall base layer I have ever used.

Rab Meco works quite well. Not quite as warm or stink proof as full merino, but it dries fast, is super thin and so far has been pretty durable (besides pilling).

"And its little brother, the Motus, which is by far the best late spring-early fall base layer I have ever used."

I found I missed the 1/4 zip in summer. The fit of the Motus, actually, is very very similar to the OR Echo L/S zip, but the OR actually has the zipper. Very similar fabrics, IMO.