High-performance recording is possible with a 3-pack of 4K-compatible 128GB BD-R XL discs. - Brand: SONY - Capacity: 128GB - Pack Count: 3 Pack - Type: BD-R XL - 4K Compatibility: Yes - Made in Japan: Yes - Write Speed: 920MB/s - BS Digital: 660MB/s - 4K BS/CS Digital: 470MB/s - Recording Type: Write-Once Since it's write-once, you can record about 8 hours of 4K BS digital content. However, you can't erase it, so it's good for recording your children's growth shot with a 4K camera, or as a replacement for old photo albums. It's recommended to record with a SONY camera and dub it through a SONY recorder. It's also good for saving memories like weddings. Thank you for viewing.