This is a package of three Blue tipped dummy rounds for the US military's aircraft-mounted, M61 Vulcan cannon. The rounds contain no powder or live primers. No holes have been drilled in the casings. Collectible and impressive inert display rounds stand about 6.5" tall.
The 20mm round is one of the Best Ammo calibers the U.S. military every introduced. Great conversation pieces, and paperweights.