If you want open-ear listening and music you can take swimming for children, choose FJX Bone Conduction Headphones; if you need compact everyday earbuds with low-latency playback for children, choose Defunc True LITE II. FJX is the more distinctive fit for active outdoor use, while Defunc is the simpler pick for ordinary listening, calls, and video.
FJX Bone Conduction Headphones vs Defunc True LITE II at a Glance
• Defunc’s biggest strength: a semi-in-ear design with Bluetooth 6.0, low-latency performance, and up to 20 hours of total playtime. Trade-off: its IPX4 water resistance is not presented as suitable for swimming.
• Choose FJX for swimming, sports, and keeping the ears uncovered; skip it if the child needs longer listed battery life or underwater Bluetooth.
• Choose Defunc for everyday music, calls, and videos; skip it if swimming-ready protection or an open-ear design is the priority.
FJX takes a very different approach from conventional earbuds. Its open-ear design sits behind the ears and uses bone conduction, transmitting sound vibrations through the cheekbones rather than covering the ear canals. That can suit a child who listens while walking, exercising, or playing outdoors and whose parent wants the child’s ears to remain uncovered. Open ears do not guarantee awareness in every situation, but the design does not seal the ear canal.
Swimming is where the feature set becomes especially specific. The headphones have an IP68 waterproof rating and built-in 32 GB storage for MP3 playback. The manufacturer says Bluetooth should not be used underwater because water interferes with the signal, so downloaded music stored on the headset is the relevant listening mode in the pool. The provided specifications list a four-hour average battery life and a 1.5-hour charge time. Those figures make charging habits worth considering for a child who expects frequent or extended use.
We compare products from their published specs and features; the verdicts below are our independent editorial opinions.
Updated: 2026-10-19 · 6 min read · Independent comparison
I would consider FJX for a family looking for sports-oriented, open-ear headphones that can also play stored music while swimming. It is a poor match for someone who wants conventional earbud sound, wireless streaming underwater, or the longer listed playtime of Defunc. The description identifies the intended age range as adults, so the data does not establish a child-specific fit; check fit and suitability rather than assuming the behind-the-ear design will work for every child.
Defunc True LITE II is the more familiar everyday option: compact, wireless earbuds with a semi-in-ear fit and touch controls. Its listed features include a 13 mm dynamic driver, Bluetooth 6.0, ENC clear calls, and low-latency performance. That combination points toward music, calls, and video on a phone or tablet. For a child who moves between schoolwork, entertainment, and casual listening, the conventional bud format may be more straightforward than switching between Bluetooth and an onboard MP3 player.
Battery life is a clear point in Defunc’s favor on paper. The product information lists 20 hours of average battery life, compared with four hours for FJX, although the supplied details do not explain how that figure is divided between the earbuds and their case. Defunc also has IPX4 water resistance. That is a useful distinction for ordinary daily use, but it is not the same swimming-focused IP68 rating FJX has. I would not choose Defunc for underwater listening.
Defunc makes more sense for families seeking the best true wireless earbuds for children in an everyday-use sense: compact buds, calls, and video playback rather than pool sessions or open-ear sports listening. Low latency is relevant for watching video and playing games, but the product details do not provide a numerical latency figure, so it is not possible to quantify the difference. As with FJX, the supplied information does not establish a child-specific fit. A semi-in-ear shape may feel different from a design that hooks behind the ears, so fit should be treated as a practical question, not a guarantee.
Side-by-Side: Which Should You Choose?
• Best for swimming → FJX Bone Conduction Headphones. It has an IP68 rating and local MP3 storage; Defunc is listed as IPX4 water-resistant.
• Best for underwater listening without a phone → FJX Bone Conduction Headphones. Use MP3 mode, since Bluetooth transmission is affected underwater.
• Best for keeping the ear canals uncovered → FJX Bone Conduction Headphones. Its open-ear bone conduction design leaves the ears bare.
• Best for calls and everyday wireless listening → Defunc True LITE II. It specifically lists ENC clear calls and Bluetooth 6.0.
• Best for low-latency video or gaming use → Defunc True LITE II. Low-latency performance is a stated feature, though no figure is provided.
• Best for outdoor sports where open ears matter → FJX Bone Conduction Headphones. The design keeps the ear canals uncovered while listening.
• Best for a conventional semi-in-ear fit → Defunc True LITE II. Choose it if you do not need FJX’s behind-the-ear, open-ear format.
One search phrase buyers may encounter is best rotatable ear cups bone conduction headphones for children. Neither product’s supplied details mention rotatable ear cups, so that feature should not decide between these two. FJX is the bone-conduction option here, but it should be chosen for its documented open-ear construction, waterproof rating, and MP3 storage—not for an unlisted adjustment feature.
In my opinion, I would buy FJX Bone Conduction Headphones for a child whose main activities include swimming and outdoor sports. The open-ear construction, IP68 rating, and onboard MP3 storage give it a use case Defunc does not match. I would choose Defunc instead for everyday calls, video, and longer listed playtime. For children who need pool-ready headphones, FJX is my pick, provided its fit and four-hour battery life suit the routine.
FAQ
The product information says water affects Bluetooth transmission and recommends MP3 mode for swimming. Its built-in 32 GB storage is intended for music played directly from the headphones.
It is listed as IPX4 water-resistant, while FJX has an IP68 rating and is specifically described for swimming. The information provided does not present Defunc as a swimming headphone.
Defunc True LITE II specifically lists low-latency performance, making it the more relevant choice for video or gaming. No numerical latency figure is provided, so the size of any difference cannot be determined from the specifications.
• Opinta Swimming Headphones vs DOOGEEEco Bone Conduction Headphones
• Altec Lansing Comfort Q+ vs iKF Open Ear Clip-On
As an Amazon Associate I earn from qualifying purchases.
We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon and affiliated sites.
When you buy through links on this page, we may earn a commission from qualifying purchases at no extra cost to you.
Amazon and the Amazon logo are trademarks of Amazon or its affiliates. This site is an independent third-party review and is not affiliated with, endorsed by, or sponsored by Amazon or the product brands mentioned.