Most float valves operate like a toilet tank with a ball going up and down with the water. These work in water storage tanks but too easily get stuck. The water level also fluctuates more than Blumats tend to like.
This one has the sensing aparatus inside a rectangular box which makes them more reliable. Outer housing molded of high impact resin. Withstands weather and abuse. Durable molded float. Two sets of brackets - fits poly tanks and steel tanks. handles up to 300 GPH inflow.