These look like the bases used on RCA "Special Red" Series premium tubes from the '50s-'60s. What a great idea! Outside diameter 1.304", inside diameter 1.190", height .879". Gold plated brass pins. Great for making your own tube adapters, test jigs, replacing broken bases on old tubes or for making your own 6L6GCs, red base 5691s etc. for a fraction of those "rip off" N.O.S. prices! Brand new production from China. This tube base fits well with the QQQ #88297 and the #8572 octal tops that we sell.