6AU6 | EF94 | 6136 | 6J4

The 6AU6 is a very popular tube found in AM/FM radio circuits. 

Equivalents & Drop-in Substitutes: 6AU6, 6AU6A, 6AU6WA, 6AU6WC, EF94, 6P2 (Russian), CV2524, 6J4 (Chinese), 6136, 7543, 8425.