Colm, I don’t own a Storejet500 but did some searches and found this : https://macbidouille.com/articles/test-du-ssd-externe-transcend-storejet-500-de-1-to-thunderbolt-et-usb-30/page2 There is a standard 2.5’’ SATA SSD inside but the SSD casing has been removed. Not sure it will fit (guess not) with casing also. The StoreJet300 has a 2.5’’ HDD (mounted in a rubber block) and a SATA SSD with casing will fit in there. I guess Dan is referring to a Transcend JetDrive which I think uses Apple’s Custom SSD’s. Good Luck