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

[This review was collected as part of a promotion.] Icebreaker gave me this free product to try, and I’m grateful they did. At first they sent me the wrong size (which I may have told them the wrong size), so they send me an updated size pretty quickly which was appreciated. For context, the second, better fitting shirt they sent me was a women’s small. I’m 5’7 and about 125lbs. The shirt was snug, but not too tight. I found the shirt to be lighter weight than I anticipated, but comfortable nonetheless. The shirt breathes well. I wore it recently for a 6 hour running race, and while I sweat through it, I definitely thought it was breathable. That said, because you can sweat through it, I wasn’t able to wear it as a single layer or outer layer in anything other than running, because I sweat too much and would have big sweat marks if I wore it alone. I did wear it under a cardigan sweater at work though, and it looked nice. When I wore it during my 6 hour race, I found that it regulated my temperature well. I didn’t ever feel too hot or too cold. The sleeves are easy to push up or pull down, and could zip or unzip to help with temp regulation as well. I wore this shirt a few times without washing it, and it definitely smelled better than any non-merino shirt I have. I found it to be similar to other merino shirts in terms of smelliness after working out in it. The fit of the shirt is good, like I mentioned above. It goes down far enough in front and back, so no wind gets up there. The sleeves are not too long or too short. Overall, it’s a really good looking shirt. Who I would recommend this shirt for: someone who is active and in changing temperatures — this is a good shirt for a late summer or early fall workout and because it have sleeves and a zipper that you can push/zip up or down, it’s great for helping you keep a good temperature. Bonus that it’s a great color and fit, so wearing it to the office is possible too if you’re in casual environment.

[This review was collected as part of a promotion.] I always struggle with the seasonal shift in temps from Summer to Fall, but the icebreaker is the perfect layer to keep me warm during high and low intensity adventures. I've been using this shirt for all my bike rides and larch marches this fall.

[This review was collected as part of a promotion.] I’ve been wearing the Women’s Oasis Long Sleeve Half Zip Thermal Top for a couple weeks and I really like it. I love the colour, and it’s comfortable, not tight and easy to move in. It’s a great layer for fall, keeps me warm without overheating. I wore it running and hiking, and it kept me warm in the cool weather but also kept me cool when I started to heat up due to its breathability. The fit is good and the half zip is handy for venting when I get warm. Disclosure: icebreaker US gave me this free product to try.

[This review was collected as part of a promotion.] I’ve been a devoted fan of Icebreaker for years, and this new half-zip merino wool shirt is a standout addition to their collection. The fabric is exceptionally soft and breathable, providing warmth without bulk. I’m especially impressed by the rich, vibrant color—it’s both sophisticated and easy to style for any occasion, from outdoor adventures to everyday wear. Best part, I can wear it for days without being smelly. Icebreaker continues to deliver timeless quality and effortless comfort.

[This review was collected as part of a promotion.] I wore this thermal top for mostly running purposes with a side of biking and casual wear. I chose to bring this top for my trail half marathon up in Aspen. During my race, I had on 4 layers: sports bra, tank top, icebreaker’s thermal top, and running vest. I sweated a lot on my back but I did not feel hot at all. I wore the top with my sleeves rolled up and it zipped open the entire time of my race. From wearing it early in the morning at high altitude to running in the noon sun, I thought the temperature control of the shirt was amazing! The shirt itself is very comfortable - super soft, lightweight and the best part was the gusseted arm pits. No pinching and good mobility while running. I think the underarm gussets make the product very unique as I don’t own any base layers cut like that. I wore a size small and it felt true to size. Easy to layer with a tank top and bra, and also perfect to wear standalone. The sleeves were a little long for me and so I had it bunched up a little. I would love this product more if it had thumb holes. One thing that did not fit was the turtle neck where it was too long up and too tight around my neck. I have a thicker neck and haven’t had too much luck with quarterzips styles. I personally had no issues with odor-neutralization, but I am not a very stinky person to begin with. It smelled good to me after my half marathon. My boyfriend has the same top but I could definitely smell his armpits after a day of wear. icebreaker US gave me this free product to try.

[This review was collected as part of a promotion.] There’s a lot of merino wool out there but just something about Icebreaker. I’ve worn their 200 Oasis Long Sleeve Half-Zip Base Layer for the past month on my outdoor adventures. It was perfect out of the box - Icebreaker’s merino wool fabric is just buttery smooth and works well with my sometimes sensitive skin. It fit true to size; I sized up one size as I personally prefer to not have skin-tight base layers. Coming in at 200 grams per square meter, this layer is perfect for those cooler fall days, but I could easily imagine it for my winter cross country skiing as well as well. During high output activities like trail running or road running, it is breathable and wicks the sweat away from my skin and any other layers I have on, which feels incredibly important as the weather cools down. After a long hike, it adjusts keeps me comfy at camp. Being able to trust in this layer keeps me feeling ready to keep pushing and training, no matter the weather or time of day. icebreaker US gave me this free product to try.

[This review was collected as part of a promotion.] Thank you Icebreaker and Expertvoice for giving me this fine product for free to test and review. I’ve been testing and reviewing gear for several years and I hope this will help others make an informed choice. I have been wearing the Women’s Merino 200 Oasis LS 1/4 zip for nearly a month. It’s been perfect for cool to cold weather. I love the feel against my skin and isn’t irritating. It’s kept me at the right temp without overheating me. The fit was perfect and not too tight. This will be great for skiing as well as a base layer or can be used alone with a ski jacket on slightly warmer days. The best part is it didn’t stink after hiking and sweating at points. I hate it when my hiking tops stink. All in all a solid top with a beautiful color.

[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.