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.
[image|1974201]
I guess Dan is referring to a Transcend JetDrive which I think uses Apple’s Custom SSD’s.
Good Luck