- description
- A subtype of [[gameplay-feature:spring-bumpers]] that uses a helical compression spring as its primary repelling force. When the ball strikes the [[gameplay-feature:bumpers]] cap, the spring compresses and snaps back, launching the ball away purely through stored mechanical energy. [[manufacturer:stoner-manufacturing-company]]'s *[[title:super-zeta]]* (1938) is among the earliest machines to feature the design. While modern [[gameplay-feature:pop-bumpers]] also contain compression springs to reset their solenoid plungers, the historical meaning — a spring that directly propels the ball without electrical power — is the defining characteristic for cataloging purposes, placing these bumpers squarely in the [[technology-generation:electromechanical]] and pre-electronic eras.