Mine are long gone but thanks
@Zeus.
From my experience and knowledge of this side of things.............
Auto Aqua - who make the h2ocean compact auto top-up (repackaged and sold by D-D in the UK) make/used to make a model called the AutoAqua Smart ATO Micro which is still around, D-D got the UK rights to those a few years ago too so prices went up.
The 'Smart ATO Micro' uses a blue light to indicate it's on, has a smaller sensor but was only single optical. I think this one is being pushed out of the market and can only assume it's due to the other version and some of their new products becoming available, although strangely the price for this went up when the lite came out.
I've owned both and never had a problem, I was one of the most weary after going bells and whistles with the Tunze Osmolator with my old marine, this has both optical and float but unless you have a sump this would never fit.
The 'h2ocean compact auto top-up' has a bigger/chunkier sensor but also has dual optical sensors, the light on this one is green.
If you're willing to wait a little while or even just buy it without the D-D repackage then the 'h2ocean compact auto top-up' you will be able to get from ebay without lining the pockets of D-D but just under the name of Auto Aqua smart ATO lite - I assure you it's exactly the same product but take a look at the links below to see for yourself.
www.theaquariumsolution.com
www.autoaqua.com.tw
It was the only thing I could find to keep a minimal rim-waterline after ages looking and several worked for me without fault.
Keep the sensors clean is something I would point out as important and removing limescale and scum from time to time is a must if you want this to last and most of all be reliable.