The 6L6 is a beam pentode with full ratings to 15 MHz. Commonly used as a modulator and low power RF amplifier. Originally a metal tube it was cloned into several glass versions: 6L6G, 6L6GA, 6L6GB and 6L6GC. The GB and GC were the same size. Another varient is the 6L6WGA/5932 which was designed for high mechanical shock and vibration.
(6L6)Length = 4.00" Diameter = 1.50"
(6L6G)Length = 5.00" Diameter = 1.87"
(6L6GB/C)Length = 3.75" Diameter = 1.37"
(6L6WGA)Length = 3.62" Diameter = 1.62"
Max voltage = 350
Max current = 67 ma
Fil voltage = 6.3
Fil current = .9 amps