Here is a new old stock, new in box RCA 2D21 tube for your equipment needs.  Top Slant D Getter.  Code 9-43 stenciled on glass.  I don't think this 
tube has ever been used as was very tightly packed in its box and packing material, very clean as well.

Shipping is USPS Ground Advantage with tracking in the United States; Priority Mail delivery is an option.  International sales via International Shipping service.  
Package weighs six (6) ounces.

Combined shipping always welcome.

TUBES ARE GUARANTEED GOOD AND IN WORKING ORDER AT SHIPMENT. TRANSIT VIA POST CAN DAMAGE TUBES.  THIS IS NO FAULT OF OURS BUT THE THIRD PARTY ENTITY 

THAT IS DELIVERING ITEM(S) TO YOU, I.E, USPS, UPS, FEDEX, YOUR NATIONAL CARRIER IF INTERNATIONAL, ETC. PLEASE INSURE THEM! WE CANNOT GUARANTEE FAILURES 

ON YOUR EQUIPMENT AFTER POWER UP AS THERE IS NO WAY TO ASCERTAIN HOW TUBES WILL INTERACT WITH YOUR ELECTRONICS; NOR IS THERE A WAY TO DETERMINE 

WHETHER THEY MAY HAVE FATAL FLAWS IN TUBES THEMSELVES!  THESE ARE USED VACUUM TUBES AND TIME MAY HAVE TAKEN A TOLL ON THEM OVER THE MANY YEARS 

SINCE THEY WERE MANUFACTURED. WE CAN ONLY TEST FOR THE PARAMETERS MENTIONED ABOVE IN ONE OR MORE OF THE FOLLOWING EQUIPMENT WE USE FOR 

MEASURING:  TV-7/U, JACKSON 648 & MAXI MATCHER 2.