403B=5591=6AK5 Western Electric NOS "O" getter halo 1958 

8.2ma

Gm=4800

5591=Special Quality 403B/6AK5

Recommended for

- Little Dot Mk3

- Little Dot Mk4 SE

- Grant Fidelity tube buffer

- CAD Trion tube microphone

- Miniwatt EL84 amp

- Grant Fidelity B283

- Darkvoice 332

- Yaqin CD 2