Ecotechnics Evolution Temperature and Humidity Digital Fan Speed Controllers.

Is anyone familiar with the ECOTECHNICS EVOLUTION TEMP & RH DIGITAL FAN SPEED CONTROLLERS?

I ask because I cannot find different model numbers or names
yet, on the pictures, some have four input knobs, others have five.
Some knobs are blue. Some are black.
And prices for NEW models (on ebay) range from £149 to £349
BUT I CANNOT FIND ANY DIFFERENCES BETWEEN THEM....???

I'm not confusing the fan controllers with the CO2 system.
I am talking about the system with the Thermostat and Humidistat sensors on 5 metre leads.

I don't want to pay £150 then need to buy lots of extras,
and I certainly don't want to pay £350 for something I could buy for £150.

BUT I NEED TO KNOW WHAT'S GOING ON....?
Surely there must be a difference between the £150 and £350 items?

(No shop sells different types).

no there isn't just ebay scams on trying to get you to pay over the odds, there is a 2 different version maybe more.

the only difference i see as i have both version is the minimum fan speeds is 20% on one them an 25% on the other.

so do not pay over £150 for one.