These look like the bases used on RCA "Special Red" Series premium tubes from the '50s-'60s. What a great idea! Outside diameter 1.292", inside diameter 1.150", height .619". Nickel plated brass pins. Great for making your own tube adapters, test jigs, replacing broken bases on old tubes or for making your own EL34s for a fraction of those "rip off" N.O.S. prices! Brand new production from China.