Purposebuilt holder for 21700 cells: Designed to accept 21700 batteries and serve as the device's integrated battery box for neat, secure storage and easy access. Flexible battery configurations: Supports series and parallel connections so you can arrange 21700 cells to match required voltage or capacity for your project. Durable construction: Built with strength construction to withstand repeated use and reduce the chance of damage during installation and handling. Saves space and simplifies assembly: The battery box doubles as a holder on the device, keeping batteries organized and reducing additional mounting hardware. Broad device compatibility: Ideal for circuit boards, electric toys, digital photo frames, electronic calendars, and similar digital products that use external battery packs. Practical uses Replaceable power for hobby electronics: Use the battery box to power DIY circuit boards or hobby projects where 21700 cells offer higher capacity than smaller cells. Portable consumer devices: Install in electric toys or digital photo frames to provide a removable, serviceable power source that's easy to . Backup power for small electronics: Integrate into electronic calendars or other compact products that require a reliable, compact battery holder. What you get A compact, integrated 21700 battery box that holds and secures cells on the device Compatibility with series and parallel wiring for flexible voltage and capacity options Robust construction for longterm use and reduced risk of damage during handling Suitable for engineers, hobbyists, and manufacturers needing a reliable 21700 battery holder that simplifies installation and supports multiple battery arrangements.