User blog comment:B214/Volume 23 discussion blog/@comment-82.178.74.14-20170726162517/@comment-10330822-20170726170802

They Longinus tier system is based on how strong they start off, but Longinus, and Sacred Gears in general, have an interesting trait of mixing with other abilities. Because of that, you have mid-tier Longinus, like Issei's Boosted Gear, that have mixed with other abilities were it allows Issei to challenge users of High-Tier Longinus.