I have this adapter. As Nick says (and as Bob himself says), it is more practical to have one adapter per lens, as mounting the adapter is not a fast operation. To fit it, you mount the adapter on the lens, then, using a small supplied allen key, fit a tiny 'set screw' which keeps the adapter firmly fixed on the lens. You then offer up the lens to the EOS mount. With this screw fitted, the lens will not move on the adapter and cannot accidentally come off it. It is supplied with two of these little grub screws, one for spare, plus an A4 sheet with clear instructions. Once you get the hang of fitting it, it's easy, but it's not something you want to do 'in the field'. The adapter is not cheap. I paid $150 (payment is accepted via Paypal), though its in line with other reputable adapters, such as the Cameraquest one, and Bob responds rapidly; mine was in my hands from the US in less than a week. I don't think he has any off the shelf at the moment, as his machinist makes them up in batches when Bob passes on his orders, and I know he is slightly re-designing it (there will be a reddish tint on the finish to distinguish it from the earlier model).
I think there are one or two Zeiss lenses that don't work well, but this is not due to the adapter, but to some measurements in the lens which may cause it to foul against the mirror assembly on some EOS digitals. Once again, Bob will advise.
Contact Bob for details, he is very helpful, and judging from the speed he responded to my queries, never seems to go to bed.