Icebreaker Sierra Half Zip Realfleece

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Manufacturer Description

The Sierra Half Zip Realfleece mid layer in our plush merino wool pile gives you another perfect alternative to synthetic fleece. This lighter weight top keeps you cozy (naturally) while offering decadent, stretchy mobility. Unlike synthetics, this fleece won’t hold odor, and comes with finishing details that look and feel fantastic.


  • 100% Merino Wool – 260 g/m2
  • Zip neck collar
    • 26 cm (10.2 in)
  • Interior zipper guard
  • Articulated raglan sleeves
  • Zippered stash sleeve pocket

    Left Sleeve Pocket
    • Triangle shaped – 14 cm x 24 cm x 22 cm (5.5 in x 9.4 in x 8.7 in)
  • Printed inner collar
  • Icebreaker embroidered logo
  • Measured size medium
    • Weight – 399 g (14.1 oz)
    • Center back – 74 cm (29.1 in)
    • Sleeve length – 90 cm (35.4 in)
    • Pit to pit – 56 cm (22 in)
  • Retail – $150

YMMV Review

Icebreaker has decided to take back the name fleece. Fleece in recent times has been more synonymous with garments made out of polyester and recycled water bottles. Fleece is actually a term used to describe a fabric with a soft, deep pile or a coat of wool. Last spring Icebreaker launched a new lineup of midlayers called their Realfleece collection. Midlayers with a deep soft pile made out of 100% merino wool. It took a while but I finally got the opportunity to test one out. If you are interested in learning more about wool, check out the article below.

Design ★★★½☆

I have mentioned many times that I am a big fan of wool. There are many reasons for this and if you are interested in all the positives of wool, please check out my article in the knowledge base section. The Icebreaker Sierra Half Zip Realfleece is made out of 260 g/m2 merino wool.

The fabric has a smooth feel on the outside and a soft pile on the inside. There is a zipper on the front that can be used for venting and a small pocket on the left sleeve. Inside the sleeve pocket there is a headphone port for routing your headphones up the inside.

Inside and Outside Fabric

There is also a loop sewn into the neck to control the cord. On the chest Icebreaker has embroidered on their logo. They have also printed the inside of the collar to add some style. Both the zipper on the chest and the one on the pocket are a shiny black finish that stands out.

One of the great features about Icebreaker products is the traceability back to the source. There is a unique Baa Code inside the garment that can be entered into the Icebreaker website to find out what farms in New Zealand the fabric from your garment was sourced. This particular top has a Baa Code of 45DD5E10E. If we plug it into the site below you can see what farms this top was sourced from.

Fit ★★★★☆

The Icebreaker Sierra Half Zip is a semi-form fitting top. The fit is not skin tight but also not lose either. I can comfortably layer it over the top of a t-shirt or long sleeved base layer. Since it is not very thick it can easily fit under a jacket if needed. The arms are a good length and so is the body. I normally wear a medium and that is the size I wear in this top as well. All in all everything fits as it should, not tight but not loose either. Even at the cuffs and around the neck, the Sierra Zip fits well.

Performance ★★★★☆

I have been really happy thus far with the performance of the Icebreaker Sierra Half Zip Realfleece. I have worn this around town and up in the mountains both with great success. The top is sharp enough to look good with a pair of jeans and technical enough to pack up into the mountains as a midlayer. I wore it on top of my Chase Zip on a trip up to Demaris Lake in the Central Oregon Cascades and I did not need my coat because I was plenty warm with this on. The Sierra Zip is a tight knit that can shed a light wind but anything significant will get through. At 260 g/m2 this is about the same thickness as a lightweight fleece but with more warmth. This top can be worn equally well over the top of a baselayer or on its own as it feels soft next to the skin. I like having the zipper in the front to allow for venting when it gets warmer.

Unlike some of the other midlayers by Icebreaker the Sierra Half Zip does not have thumbs holes. Overall the durability of the top has been good even when worn under a pack. The only issue I have noticed is that the seams seem to fluff up easily. I have tried to show this in a picture as it is really a small thing and by no means affects the performance or functionality of the garment. I like the pocket and headphone port in the sleeve pocket but the pocket is a weird shape.  I wish it could have been made a bit more square. The current shape does limit what it can carry.

Seams Fluff Up a in a Couple Places

Overall ★★★★☆

Even if I do not think about all the qualities that I like about wool, the performance of this top is worthy of this rating. The Sierra Half Zip Realfleece has excellent warmth to weight ratio. It manages moisture and does not smell over long periods of time. The other great thing about this top is how versatile it is. As mentioned above you can wear it on the trail and then out to dinner. It looks like now there is some real competition for those plastic fleeces on the market. If you want a high quality fleece that you can feel good about, check these out. At $150 they are a bit expensive but will last a long time if taken care of. As always, your mileage may vary.

Front Zipper - Oooh Fancy!


  • 100% Merino Wool
  • Soft against the skin
  • Traceable


  • Expensive
  • Fluffs up around seams easily


About the Author

I am an avid runner, cyclist, swimmer, hiker, climber, skier and many other activities that would make this list too long. I started Your Mileage May Vary Reviews in Early 2011 to combine two of my passions: sports and gear.

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