Tung Sol 5881 Power Tube
The Tung Sol 5881 Power Tube is a reliable, general purpose power tube.
The tube is a 23 watt tube and is rated for a maximum plate voltage of 400Vdc. Many amplifiers that have higher plate voltage but use a tube rectifier can use the Tungsol 5881 tubes without issue.
Refer to the data sheet for more details.