Hard Drive Shucking
Hard drive shucking is removing the internal drive from external HDD units to use them as internal HDDs or for NAS setups. The reason for this is simple - it's a lot cheaper. Shucking an 8tb WD elements drive can save you £50 over buying WD Red. I did this for my home NAS.
If you're in the US, the WD Easystore seem to be a go-to option for shucking. Outside the US, WD Elements are similarly easy. I wouldn't recommend shucking any WD drive under 8tb because you are likely to get a bad HDD. There haven't been any reports of getting bad HDDs from 8tb+ WD external drives. Other brands than WD can be shucked but it's more difficult.Youtube Video on Shucking WD elements
Reddit thread on Shucking Easystores