An ultra-high velocity (CCI calls it Hyper Velocity) .22 round. It uses a slightly shorter 32 grain projectile, and a slightly longer case for a bit more powder. Thus the over-all length is the same, but it is not exactly a .22LR round even though it will fit in many chambers, because it won't in others due to not following the established LR specification.
Apart from sizing issues, the extra energy is not recommended in some firearms. Too much power for the recoil springs, bolts cycling too hard.
But they're fun, effective rounds in many rifles.