Arc'teryx Rho LTW Beanie

Simple, light weight Beanie
Compare to the Arcteryx Bird Head and classic Beanie, the Rho LTW Beanie feels different. First of all, its very thin and stretch well which, for me, is a plus. They do feel comfortable and cozy unlike the other 2 beanie which feels tight. Performance wise, due to its thickness, the Rho beanie doesn't provide as much warmth as the Bird head or classic Beanie. Build quality is very good and it has a simple and timeless design. I would recommend this beanie to anyone in cool weather / morning. However, it may not provide the needed warmth in cold winters

Perfect
Perfect hat for all outdoor athletics - not too heavy but definitely warm enough for most activities above 30 degrees

Always have it with me
I had it for over a year and just got another one. I use it for cycling and just around. Perhaps if you want something for very cold days with freezing wind it might be too thin. I often combine it with hood in the coldest days in Boston when I commute on a bicycle. I found it useful all year around. Good for running, very breathable, highly recommended.

Thin and light, feels tight and nice
This knit is finer than my icebreaker stuff and doesn't itch at all. The icebreaker hat itches a little bit. This thing packs down to almost nothing and stows in the pocket easily. My head is 23 inches or 59 cm and it fits perfectly. Just barely covers both my ears. It's more like a skullcap. It fits like one of those gangster type pantyhose skull caps, that fit under helmets, but it is so much nicer than those cheap nylon doo rag things. I recommend it and I want another as a back up. Good looking out, Altrec and Arc'teryx.

Very Lightweight and strechable beanie
As others have noted, this is lightweight, comparable to my Icebreaker 150 weight merino, or less. It's a little more elastic/stretchy than my other merino beanies, but this one is great when it's not that cold outside. The thin merino does well even in the summer, under a helmet or by itself, to help wick away moisture and let it evaporate. A little on the large size for my 58cm/ 22.75" head circumference, and I normally wear a medium to large size hat or helmet. I wish it fit a little snugger. Always feels loose, and it will ride up on my head, if I'm not careful. One thing to note, is that this Merino fabric is less itchy than other merino I have. It's has a nice weave.