These are commercial short bottle tubes from the 1960's with triple layer top mica and open top halo getter! Both test strong and VERY Tightly Matched with only about 1% difference between them in both Gm and current draw in our equipment! 

This set looks also just like the day they were made with excellent lush silver flashing and clean shiny bases (little tiny scratches). We've auditioned these in both of our amplifiers and they're fantastic performers with excellent detail, nice clean highs, a superb mid-range, good solid bass and loads of headroom! Nice sounding powerful tubes when run both in my stereo and my guitar amp! Test results are below.

Compatible and safe to use in all 6L6 type amplifiers including 6L6G, GB, GC, as well as KT66 and 7581 amplifiers with no mods needed. From personal experience, vintage USA tubes will outlast Chinese and Russian tubes by 3 to 1 (and sound SO MUCH better too).

Sold as is, guaranteed as described.

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