SM-FOZ-41XX Side Entry Float Switch - Rochester Sensors
HALJIA 2PCS ZP4510 Mini Liquid Water Level Sensor Vertical Float Switch Tank Liquid Water Sensor Floating Switches for Aquarium Pump Control L = 45mm : Amazon.co.uk: Business, Industry & Science
Small Float Switch for Tanks - Fill or Empty
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Guide to Using Float Switches in Water Tanks | Tameson.co.uk