I wanted the E-Bike version but apparently there’s only one shop in the UK that sells Rex , they only had the regular Black Diamond and the Domestique. I plan on picking up an ultrasonic cleaner too, looking for a compact one that I can still fit the cassette in.Rex representative told me that the difference between Black Diamond and the E-version of it is in amount of anti wear additives. E-version is not as watt optimized as regular Black Diamond (not far from it but when in seek of ultimate efficiency regular is better). There is no solvents in Rex chain lubes so do not over use it! Everything you add to chain will stay there! I was willing to go the extra mile and did the ultrasonic cleaning to chain prior to first application.
It's crazy how long Rex Domestique and Black Diamond lasts when it's dry weather. You can go hundreds of kilometers easy. I did 150 km continuous training with "cheapest" Domestique and no chain noise at all for that day!