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Heatwave Thermalwear

Kids Winter Thermal Underwear Set Boys Warm Long Sleeve Top and Pants Cozy Insulating Base Layer Sizes 3-13 Charcoal Black by Heatwave Thermalwear

Regular price £7.00 GBP
Regular price Sale price £7.00 GBP
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Heatwave® Boys Thermal Long Sleeve Top & Pants Set, Kids Warm Winter Underwear

Introducing the Heatwave® Boys Thermal Long Sleeve Top & Pants Set, the ultimate winter underwear solution for kids. Designed to provide superior warmth and comfort, this set is ideal for cold winter days, ensuring your little one stays snug and cozy. The unique 0.45 tog rating sets it apart, providing excellent insulation by holding more warm air close to the skin.

Key Feature 1: Advanced Insulating Yarn

Description: The thermal underwear base layers are crafted from an advanced insulating yarn. This material boasts high performance insulation with a soft brushed inner that enhances warmth.


  • Keeps your child warm by trapping heat close to the body, perfect for outdoor activities or cold indoor environments.

Key Feature 2: Comfort Fit Design

Description: The ribbed construction of the set shapes to the contours of the body, offering a perfect fit. The tops are side seam-free, adding an extra layer of comfort.


  • Provides a snug and comfortable fit that moves with your child, reducing discomfort and allowing free movement.

Key Feature 3: High Performance Insulation

Description: The combination of 50% polyester and 50% cotton provides excellent insulation while maintaining breathability. The materials are specifically designed to keep children warm without overheating.


  • Balances warmth and breathability, making it ideal for both indoor and outdoor use during the winter season.


  • Ages 3-5: Long Sleeve Top Chest to Fit Approx 20-22", Long John Pants Waist to Fit Approx 20.5"
  • Ages 6-8: Long Sleeve Top Chest to Fit Approx 24-26", Long John Pants Waist to Fit Approx 21.5"
  • Ages 9-11: Long Sleeve Top Chest to Fit Approx 28-30", Long John Pants Waist to Fit Approx 22.5"
  • Ages 12-13: Long Sleeve Top Chest to Fit Approx 30-32", Long John Pants Waist to Fit Approx 24.5"

Colours Or Style Options

  • Black
  • Charcoal

Care Guide

  • Machine washable at 40°C
  • Can be tumble dried
  • Wash dark colours separately

Why Choose This Product

Choose the Heatwave® Boys Thermal Long Sleeve Top & Pants Set for its superior warmth, comfort fit, and high-performance insulation. Unlike other winter underwear, this set is designed with both warmth and comfort in mind. User testimonials praise its durability and effectiveness, making it a reliable choice for keeping your child warm during the cold months. Trust in the quality and value of Heatwave® for a worry-free winter experience.

Additional Information

Usability: Ideal for outdoor play, winter sports, or as an extra layer under school uniforms. This versatile set ensures your child stays warm in various settings.

Warranty and Support: Comes with a satisfaction guarantee and responsive customer support. Return policies are in place to ensure you are completely satisfied with your purchase.


We have partnered with 20 innovative grassroot companies that we believe can help reverse climate change. We allocate a fixed margin from every sale to support fund nature-based carbon removal solutions such as reforestation and soil carbon sequestration. Fund companies such as DroneSeed, Grassroots Carbon, and Pachama.

We are committed at Sock Stack to neutralize our shipping emissions and remove carbon dioxide from the atmosphere. Learn more here.

We also work closely with Royal Mail to ensure hassle-free, on-time delivery. Generally processing times are within 1 business day*. Processing times may also be extended during holidays, launches/re-stocks, limited edition releases and promotions. We will notify you as soon as your order ships or if we foresee any issues with fulfilling your order. Read our full Shipping Policy for more information.
*Please understand that business days do not include weekends and Bank Holidays (United Kingdom).

£3.95 flat fee for all domestic within the United Kingdom (free shipping over £40), 2-4 working days.
£5.95 express fee for all domestic within the United Kingdom, 1-3 working days.

Easy returns

Not completely satisfied with your purchase? Reach out within 35 days to explore hassle-free return options. We've simplified cancelations for a full refund and additionally return requests can be made from your online account. Please review our Refund Policy for more details. Thank you for your patience and understanding as we navigate this together.


Sock Stack does not have a call centre and we're not set up to handle high volumes of phone calls.

The Sock Stack brand was built online, including our customer support. Though you may receive an automated response every once in a while, all channels are manned by human staff who are eager to help you out, quickly and efficiently.

Thank you again for visiting Sock Stack. For information on our new product launches, please follow us on Instagram & Facebook. For customer service inquiries, please send us a message on Facebook Messenger or e-mail us at For order inquiries, please include your order number for faster service.


Clearpay makes budgeting easier, allowing you to break down your payments into four installments, due every two weeks, interest free. Head over to Sock Stack and find something you love. Then, just add to bag and simply select Clearpay as your payment method at the checkout. Enjoy your new stuff right away and pay over four installments.

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Buy now and pay 30 days later with KLARNA payment portal. You get all the “closure” of a full upfront payment, but with the cash-flow benefits of spreading the cost. The total amount charged to your card is no greater than if you simply paid for the entire purchase up front.



We are a young, bold homeware brand. We’re fun, we’re social and we’re an upcoming brand that doesn’t sleep. Interested in partnering? Apply today to be part of our community.

Sock Stack

Our Mission

Heatwave Thermalwear® envisions becoming the most celebrated, trustworthy, and sought-after brand by offering superior, distinctive, and inexpensive thermal wear products that exceed every customer's expectations. Heatwave Thermalwear's® vision is to become a leading thermal underwear baselayer brand by delivering the most refined and high-grade products to the customers that are thoughtfully developed to withstand extremely cold conditions while offering enhanced protection and unmatched comfort.

Sock Stack

Function, Fit & Style

Heatwave Thermalwear® strives to provide a diverse collection of the highest quality and affordable thermal underwear to men and women. Our thermal socks, long-sleeve base layers, long johns, hats and gloves are meticulously designed to be safe, lightweight, and breathable, providing fast-wicking and added warmth. As a customer-first brand, we are committed to fostering solid and lifelong relationships with our clients and aspire to deliver exceptional quality and value in our products.

Customer Reviews

Based on 1 review
MIke wIlliams (Yeovil, GB)
Happy little chap

These were for my grandson and he couldn’t wait to wear them next day , he said he loves them and even his friends want some now. They wash well too.