The #26012 is probably the most popular automatic switch in the marine industry. And, for some very valid reasons!
The micro switch, the original and only American-made AFS, uses a specialty designed material to handle DC current; providing solid, reliable performance. Ultrasonically sealed inside the thermo-plastic housing, the micro switch activates your bilge pump with an audible "click". As water exceeds acceptable levels, the pump is turned on by a rolling steel ball that changes pressure on the micro switch. Rapid on-off cycling is prevented by a built-in differential of 1-5/8" and by an exclusive anti-spike feature.