Here's what Cioks say about the Split Flex cable:
Split Flex gives you the possibility for connecting two pedals to the power supply using one outlet only. Two cables in lengths 30 and 50cm are connected to the plug on the power supply side. On the other end they are terminated with 5,5/2,1mm centre negative angled DC plugs which is the most common type also called the BOSS standard. Both pedals connected to the power supply will be powered with the same voltage and will not be isolated from each other. Split Flex is like a 2-way daisy chain. Make sure that the sum of currents drawn by the two pedals doesn’t exceed the rating of the outlet used. We mainly recommend to use the Split Flex with two analogue low current draw pedals and 100mA outlets. Using Split Flex with two digital pedal or one analogue and one digital might generate unwanted noise in your signal. If you wish to power three pedals with the same voltage of one outlet have a look at CIOKS 3-way daisy chain Flex.