From the manufacturer:
“Ah, so you like a set of strings that packs a punch, do ya? You like to pick heavy on the bottom but still want to be able to bend up top? Well then, our Heavy Bottom 10s are just the strings for you.
This set addresses the two tension issues that arise in typical 10-52 sets: the 2nd string is too light, and the 5thstring is too heavy. We fix the top end by subbing in a .0135 for the typical .013, bringing perfect balance to all the plain strings. Then on bottom, we drop the gauge of the 5th string to a .040 (from the typical .042) to pull everything evenly together down there.
These two tweaks give our Heavy Bottom 10s great balance on both the plain and wound strings, with extra tension on the bottom for heavier players—or just those who are after a thicker bottom end sound.“