Icebreaker  200 Oasis Long-Sleeve Half-Zip Base Layer Top - Women's

[This review was collected as part of a promotion.] Disclosure: icebreaker US gave me this free product to try. ​The Women's Merino 200 Oasis Long Sleeve Half Zip is one of the most popular base layers on the market, and after extensive testing across various cold and moderate conditions, it’s clear why. This review focuses on the shirt's comfort, breathability, temperature control, odor-neutralization, and fit, with a specific focus on its performance during fisheries fieldwork. ​Field Context & Conditions: I utilized this top during a two-week stretch of stream habitat and fish population surveys in the Pacific Northwest during the shoulder season (late fall). The conditions were classic fieldwork: starting cold with high humidity, often involving strenuous hiking to remote sites, and long periods of static work (setting nets, data collection) while standing in cold water (wearing waders). ​Temperature Control (High-Output to Static): This was the Oasis’s greatest strength in the field. The initial uphill hikes to the stream required high exertion, leading to significant body heat. The half-zip design was essential here—unzipping it all the way provided immediate, necessary ventilation, preventing the "sweat out" that leads to post-exertion chill. Once at the stream, standing stationary in chest waders for hours, the 200-weight merino efficiently trapped heat, keeping my core reliably warm, even when my outer wader layer became slightly damp from splashing. Merino’s ability to insulate when slightly wet is critical for any job near water. ​Odor Neutralization (Multi-Day Use): For extended fieldwork involving camping or remote lodging with limited laundry access, the odor-resistance was a non-negotiable feature. I wore this shirt for four consecutive days without washing, and it maintained an impressive neutrality—far superior to any synthetic base layer I have ever used. This single attribute significantly reduces the amount of gear a field biologist needs to pack. ​Comfort and Fit under Layers: When layering heavy, protective gear—like a fleece mid-layer and a waterproof wading jacket—comfort is paramount. The flatlock seams and soft merino fabric (no itchiness) meant zero chafing, even when compressed by backpack straps and life vests. The slim fit allowed the top to slide smoothly under bulkier garments without bunching, maintaining mobility for tasks like electrofishing or net hauling. ​Area for Improvement ​Drying Speed: While the merino insulated well even when damp, it is not the fastest-drying layer. On one particularly wet day, after the top absorbed some moisture (both sweat and humidity from inside the waders), it took a full overnight hang in a non-heated cabin to completely dry. For fast-paced, multi-day work where you might need to wash and re-wear a layer daily, a merino/synthetic blend might manage liquid moisture faster. However, for sheer warmth and comfort, the 100% merino is a winner. I wish the Oasis incorporated some targeted synthetic zones (like the underarms) for ultra-fast wicking in high-sweat areas, without sacrificing the overall wool comfort.

Originally posted on ExpertVoice.com

[This review was collected as part of a promotion.] My icebreaker wool base layer is awesome! So far I have used my base layer on a bike packing trip across the Netherlands over 4 days this week (~30miles/day). In the chilly, breezy weather of the Netherlands (high only ~60 each day), it kept me warm and dry. Even though I did sweat my IceBreaker wicked away moisture so I stayed warm even in the wind. The best part is that it's so comfortable to wear! I was worried it would be itchy as wool tends to be but the fine weave of the fabric made it feel SO soft against my skin. I didn't even wear a cami underneath, just a sports bra. In addition, it doesn't seem to hold an odor even though I sweat in it. The fit is also great, not too loose or too tight but just perfect. I highly recommend the IceBreaker wool base layer! Please not my pictures are from day 0, our trial and warmup day so I did not have my paneers on my bike that day

Originally posted on ExpertVoice.com

Yes

[This review was collected as part of a promotion.] We loved our icebreaker merino gear for our fall hiking. It was wind-blocking, too. Cooler nights and layering was the name of the game this September in Glacier. This top made my nighttime outfits easy to plan. When you’re backpacking, one and done is necessary for your next to skin layer. I love merino because it’s so soft! I fell asleep in it one night! We are super stoked on the colors this time around, as well. Good job icebreaker. The ice is broken. Warmth from here on out

Originally posted on ExpertVoice.com

Excellent base layer and I love the color

[This review was collected as part of a promotion.] Icebreaker products are just very good. I have baselayers I bought years ago that held up really well and are warm and so light and thin and efficient. Plus I love the new and more interesting colors than the older always black base layers. Anyway this is a very good product and I don't give complements easily it just isn't cheap. But you get what you pay for, right? So yes I would buy them again, except these will last a really long time and keep me nice and warm. My only suggestion is they could add a touch more stretch to the wonderful merino wool fabric. 5% more spandex would be great.

Originally posted on icebreaker.com

Great base layer

I really liked the fabric weight and color of this base layer… I docked it a star because it doesn’t quite make 5stars due to the zipper placard which is just a bit bigger and stiffer than I’d like. Additionally the collar is just a bit too heavy for some reason. I have one almost exactly the same from Arc’teryx that does it just a little better… was hoping to love this one as much as but sadly it’s not as good.

Versatile layer

[This review was collected as part of a promotion.] I like the versatility of the half zip and the weight of this thermal top. I wear it on runs, hikes, and even bikes around town. It looks nice enough for daily wear and it is functional enough for active pursuits -- so it's great if I have something social post activity. The colour is so pretty too! After initial wash, it felt snug but then loosened up. Very happy with this purcahse!

Originally posted on icebreaker.com

Effective heat and moistire management. Not the #1 softest wool

Functions well, as expected from merino wool. Thin, but a great base layer or worn alone in all temps. I use it for high intensity xc skiing and hiking. Beautiful, vibrant color. (Hard to find vibrant wool colors.) Gave it 4 imstead of 5 stars because it isn't soft enough to sleep in when camping. Nothing beats my Smartwool for that perfect comfort

Originally posted on ExpertVoice.com

I bought this several months ago and have gotten a lot of use out of it this winter. I ordered the bottoms as well. This was my first experience with Icebreaker products and I am impressed! High quality, comfortable, and fits true to size. It made an excellent base layer on cold days!

Originally posted on ExpertVoice.com

Poor Quality Material

Warning you not to buy it. Wore it three times, washed it once in cold water and hung it to dry. It immediately got a hole in the right shoulder. Yes, it is lightweight merino, but it shouldn't be tissue thin and developing holes after the first wash.

Comfortable and Versatile pullover

[This review was collected as part of a promotion.] My black version of this half-zip has been a staple for everyday, travel, golf, etc. I was excited to see it in this beautiful Carolina blue shade and find that it fits as perfectly as my original one! Can't beat this pullover for layering versatility!

Originally posted on icebreaker.com