Eurotubes &ldquo;EuroDamper&rdquo; Tube Damper Rings for Octal Base Power and Rectifier Tubes. Set of 4. Custom made from special soft durometer hi-temp silicone These will reduce or eliminate tube rattle in most all combo amps For Octal Base Power Tubes including EL34, 6L6, 5881, KT77 Largest and most effective vacuum tube dampers made Will not fit 6550, KT66 and KT88 power tubes