Thanks for the replies which have both really helped. I realise that Apple stuff is rarely simple and it's taken me a while to tease out the details of this. I think my mini is the standard late 2012 configuration, with the original HDD fitted just under the antenna grid. This is the lower bay I think. Anyway I used the I Fixit guide, amongst others, to add the SSD, and I've now found the I Fixit part number for their cable - 076-1413. PowerbookMedic lists 076-1413 as having 2 alternative part numbers - 076-1360 and 076-1391. So it looks a like I'm right. PowerbookMedic describes 1412 as for a lower bay, mini server. The Amazon seller I bought it from had customer reviews saying it worked fine and there are a fair few Amazon UK sellers and they all offer 1412, And finally, my unibody number is different. The listings all give it as 821-1501-A, but mine is 810-4468-A. PowerbookMedic lists it, but says nothing more about it. Should I buy cable 1413?