Davis Emergency Radar Reflector 
Emergency Radar Reflector
Every small boat needs a radar reflector. The Davis Emergency Radar Reflector is a compact, lightweight and economical unit that disassembles and stows flat for storage. When needed, it pops open to 11.5" diameter (29 cm) and installs in seconds. Its three perpendicular planes reflect radar from all directions.
Made of special plastic-metal foil laminate. Resists corrosion and peeling.
Owner's Manual (pdf)