adapter-with-ecc99 Published July 6, 2016 at 1600 × 862 in Gilmore Jr. Two Watt Mod 2 Watt Mod Adapter showing size with ECC99 vs size with 5751, 12AT7, 12AU7, 12AV7, (never use 12AX7!) Share This! 2 Watt Mod Adapter showing size with ECC99 vs size with 5751, 12AT7, 12AU7, 12AV7, (never use 12AX7!) Share This!