You might not think you need this but you probably will
This little adaptor will allow you to run anything which requires a +5v power supply on one power rail of your modular case. I bought it because it was required for an oscillator which I purchased, but it can have many applications. My next use for it will be to power LED lights to illuminate my modular in gig situations. You simply connect the adaptor to a spare connector on the rail which you will need it, and then you have +5v power available for all the other connectors on that rail. My one reservation is that this could have been a little bit cheaper for what it does, or alternatively Doepfer could just build this provision into their modular cases as standard. After all a P9 case, for example, is not cheap and when you have spent that amount of money you kind of resent having to buy this.