These stainless-steel slugs fit the NATO 5.56 counterweight box.
The 5.56 counter-weight box was designed to fit your standard NATO 5.56 (.223) round. However, these provide twice the weight (10x standard 5.56 rounds is 4oz, and these clock in at 8oz for a set of 10) and also have the added bonus of being air-travel friendly.
The combined weight of the 5.56 counterweight box with (QTY:10) 5.56 rounds is 8oz. The combined weight of the 5.56 counterweight box with 10 of these slugs is 12oz.