Just had a root through the shed as I had one of these that I never used on my Diabolous cranks but sadly it seems to have gone out of the box it was in. Chainreaction used to do them as did ukbikestore.
Very wise as I'm only saying what the instructions say, these are modern things and I've never had one. I stop at Turbine LPs though I have dabbled into ISIS fitting ;-)
I believe its so there is a neater setup for double or single ring setups.