Norris Spring for upright and grand pianos, made of spring steel.

584A-7/8"
584B- 1-3/8"
584C- 1-7/8"
584D- 3-1/2"

Specialized coil spring used in piano hardware and pedal mechanisms, commonly installed on trap levers or foot pedals to help return the pedal rod and trap work to their resting positions.