The 6AU5GT is described as a beam pentode and was designed for line output service in television receivers. An alternate design use is as a series pass device in regulated power supplies.

The grey anode allows greater heat dissipation by radiation than a bright metal anode. The 6AU5GT has a 10 Watt anode dissipation.

The top view shows the heat sink fins attached to the grid support rods.

The wide glass tube envelope is 29 mm in diameter, and excluding the IO base pins is 65 mm tall.

Reference: Datasheet. Type 6AU5GT was first introduced^¶ in 1949.

 
Pin Connections

IO	1	2	3	4	5	6	7	8
	g1	h	k,g3	-	a	-	h	g2

 
Absolute Maximum Operating Conditions^¶

Pentode	Vh	Ah	Va	Vs	Vg	mAa	mAs	ra	gm
	6.3	1.25	550	200	-45	110	-	6,000	5.6

Thanks to Frank Philipse for supplying the above PDF datasheet