New from Marui, the "Perfect Hit" BBs are actually about 5.95mm in diameter and made with the very same process as their bearing manufacturing. This makes the BBs slim, consistent and high quality enough to be used in tightbores as low as 6.01mm as suppose to other BBs which might vary enough in diameter as to cause inner barrel abrasion or jamming.
At 0.20g, these BBs are best used in assault type weapons looking to get more FPS with larger volume fire. While heavier pellets are more stable in flight and thus better for longer range weapons, the lighter 0.20 is the lightest BB usable to maintain stability and offers more FPS on the same spring when compared to a heavier pellet. With these pellets, you can now install a 6.01mm tightbore on your assault weapon and not worry about barrel wear!