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Short answer: Both hold 10 oz. The Thermos FUNtainer has a push-button lid that kids can open easily, a folding spoon stored in the lid, and top-rack dishwasher cleaning, and it’s rated “up to 5 hours hot.” The Zojirushi SW-KA30 has a leak-proof one-piece stopper and a pressure-relieving lid, and Zojirushi lists it at 136°F after 6 hours.
How we compare: every spec in this article comes from official manufacturer specifications and manuals (starting with Zojirushi’s official product page and Thermos’s official product page), all listed under Sources below. We don’t run hands-on tests, and if a spec isn’t published, we say so. Last updated: October 2026.
I live in Japan. School lunch in Japan is usually served at school, but home-packed lunches for outings are a ritual. These are the two 10 oz jars US parents usually look at.
I haven’t tested these side by side. Everything below comes from the manufacturers’ official product pages, linked at the end. If a spec isn’t published, I say so instead of guessing.
Quick Comparison Table
| Spec | Zojirushi SW-KA30 | Thermos FUNtainer 10 oz |
|---|---|---|
| Capacity | 10 oz / 0.30 L | 10 oz (290 mL) |
| Dimensions | 3-7/8 x 3-7/8 x 4-3/8 in (W x D x H) | 3.5 W x 3.7 D x 5.3 H in |
| Weight | 0 lb 11 oz | 0.6 lb |
| Heat rating | 136°F after 6 hours* | Up to 5 hours hot |
| Cold rating | 50°F after 6 hours* | Up to 7 hours cold |
| Lid | Therma Chamber lid, leak-proof one-piece stopper | Push-button lid |
| Spoon | Not listed | Folding spoon stored in lid |
| Opening | 2-7/8 in | Wide mouth (width not listed) |
| Dishwasher | Not listed | Top rack only |
| Made in | Thailand | China |
*Zojirushi rates heat retention with 203°F (95°C) water in a 68°F (20°C) room, and cold retention with 40°F (4°C) water in the same room.
Key differences at a glance
- Lid: The FUNtainer has a push-button pop-up lid for young kids, while the SW-KA30 has a screw-style one-piece stopper.
- Heat rating: Zojirushi lists 136°F after 6 hours, while Thermos lists “up to 5 hours hot” without a temperature.
- Shape: The SW-KA30 is short and wide at 4-3/8 inches tall, while the FUNtainer is taller and narrower at 5.3 inches.
- Weight: The FUNtainer weighs 0.6 lb (about 9.6 oz), while the SW-KA30 weighs 11 oz.
- What stays the same: Both are double-wall vacuum-insulated stainless jars with a 10 oz capacity.
The 4 Differences That Matter
1. Kid usability
A push-button lid that pops open is the FUNtainer’s main selling point for young kids. The SW-KA30 has a screw-style lid with a one-piece stopper, which suits older kids and adults.
2. Heat rating
Zojirushi: 136°F after 6 hours. Thermos: up to 5 hours hot, with no temperature given. They aren’t the same kind of rating.
3. Shape
The SW-KA30 is short and wide (4-3/8 in tall). The FUNtainer is taller and narrower (5.3 in).
4. Weight
0.6 lb (about 9.6 oz) for the Thermos vs 11 oz for the Zojirushi.
What’s the same
Both are double-wall vacuum-insulated stainless jars with a 10 oz capacity.
Who Should Buy Which?
Choose the Zojirushi SW-KA30 if you:
- Want the leak-proof claim
- Want a published 6-hour temperature
- Have an older kid or are packing for yourself
Choose the Thermos FUNtainer 10 oz if you:
- Have a young child who opens it alone
- Want the spoon included
- Want dishwasher cleaning
Kids’ Food Jars in Japan
Japanese school lunches are usually provided, but soup jars are common for packed lunches and outings. Zojirushi Japan sells the SW-KA30 under that same number: 300 mL, suggested for miso soup, with a 7 cm mouth, rated at 58 °C or higher after 6 hours and 10 °C or lower cold, in ice gray, matte green and beige. Thermos Japan has sold its own soup jars, such as the 500 mL JEB-500, now discontinued. The FUNtainer line is a US-market Thermos product.
Japanese reviewers on Rakuten and Kakaku.com often say the SW-KA keeps soup warm until lunch, especially if the jar is preheated with hot water, and like its wide mouth and few parts; one recurring gripe is that the large lid is hard to open one-handed. (Third-party reviews, not our own testing.)
For older kids or adults, the next sizes up are compared in SW-KA40 vs SW-KA52.
SW-KA30 vs Thermos FUNtainer 10 oz: Frequently Asked Questions
Is the FUNtainer dishwasher safe?
Thermos says top rack only.
Is the SW-KA30 leak-proof?
Zojirushi says yes, when used according to the instruction manual.
Which keeps soup hotter until lunch?
The ratings can’t be compared directly. Zojirushi lists 136°F after 6 hours; Thermos lists up to 5 hours hot.
Do both hold 10 oz?
Yes.
Check current listings
Prices and colors change often, so check the current listing before buying.
Related comparisons
- Zojirushi SW-KA40 vs SW-KA52: 14 oz or 18 oz Food Jar?
- Zojirushi SW-EAE35 vs SW-EAE50: 12 oz or 17 oz Food Jar?
- Zojirushi SW-EAE50 vs Thermos Stainless King 16 oz: Which?
- Thermos FUNtainer 10 oz vs 16 oz Food Jar: Which Size?
Sources
- Zojirushi, Stainless Steel Food Jar SW-KA30/40/52 (official): https://www.zojirushi.com/app/product/swka
- Thermos, 10oz FUNtainer Food Jar (official): https://thermos.com/products/funtainer-r-stainless-steel-food-jar-10oz
- Zojirushi Japan: SW-KA soup jar specs (zojirushi.co.jp): https://www.zojirushi.co.jp/syohin/bento/soup_jar/sw-ka/
- Thermos Japan: JEB-500 soup jar specs (thermos.jp): https://www.thermos.jp/product/detail/jeb-500.html
- Rakuten user reviews: Zojirushi SW-KA40 (Japanese): https://review.rakuten.co.jp/item/1/405752_10000164/1.1/
- Kakaku.com: Zojirushi SW-KA40 reviews (Japanese): https://kakaku.com/item/K0001480100/
Specs checked October 2026. Prices and availability change, so check the current listing before buying.
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