The Pre-built models have a fixed amount of storage and use M.2 2280 PCIe Gen 4 SSDs. The Performance and Performance Pro variants come with 512GB, while the Overkill variant has 1TB. Pre-built variants all come with Western Digital PC SN810 drives. There’s a second M.2 slot using the smaller 2230 format; see the layout
here.

The DIY variant has many storage options, including:

• 250GB WD_Black SN770
• 500GB WD_Black SN770 
• 1TB WD_Black SN770
• 1TB WD_Black SN850X
• 2TB WD_Black SN770
• 2TB WD_Black SN850X
• 4TB WD_Black SN850X
• None (bring your own)

The secondary storage options include:

• 250GB WD_Black SN770
• 1TB Western Digital SN740
• 2TB Western Digital SN740
• None (bring your own)

The SN850X drives are the fastest; the performance of the the SN770 and the SN740 is the same for 1TB capacities and above. However, the smaller 500GB and 250GB SN770 drives perform worse. If you primarily game, the differences are mostly negligible. However, if you transfer a lot of files locally, the difference in performance will be more noticeable; see the SN740’s specifications, SN770’s specifications, and SN850X’s specifications.

Finally, you can add additional storage with Framework’s expansion cards, which use a USB 3.2 Gen 2 interface. There are options for 250GB or 1TB cards; Framework advertises up to 1000 MB/s read and 800 MB/s write speeds for both capacities.