An internal hard drive bundle contains 2, 3, or 4 HDDs. With a 3.5-inch HDD bundle, you can expand the storage capacity of your computer or NAS. Let these drives work together in RAID mode to make them faster and/or safer. For example, rotate 2 hard drives in RAID 0 if you want to transfer files faster or rotate them in RAID 1 to store files twice as safe. Do you want a bundle with 3 hard drives? It's best to set RAID 5 to keep files even more secure. And with 4 drives, you can choose the best for RAID 10. This saves files both faster and more securely. A RAID setup ensures a lower total storage capacity. If this is a problem, install them without RAID to create the maximum storage space. Or choose internal hard drives with a higher storage space, such as 4TB, 6TB, or 8TB. When purchasing a bundle, make sure your NAS system or desktop has enough slots for these drives.