Add to Cart Quick view RCA 5557 New in Box Thyratron Mercury Vapor Triode RCA MSRP: Now: $99.99 Was: This RCA 5557 New in Box Thyratron Mercury Vapor Triode, is a rare find. Newer versions of this tube do not have the quality of this original RCA. Description 5557 THYRATRON TUBE HIGH SENSITIVITY SPARK PROTECTION TUBE FOR HIGH FREQUENCY MACHINE... MSRP: Now: $99.99 Was: Add to Cart Quick view Qty in Cart: 0 Quantity: Decrease Quantity: Increase Quantity: Price: MSRP: Now: $99.99 Was: Subtotal: Add to Cart