There has never been a more hotly anticipated sub-load than the Costa Leg Rig. It was so hotly anticipated in fact that the first run of them sold out in hours. So, while these are unavailable right now, it is nice to finally have the details.
I have tried to like magazine sub-loads before but they all sat too low on the leg which brought a host of problems. The Costa Sub Load is designed to rid higher and utilizes two hangers so it is more stable on the belt. It certainly seems to be a better approach on paper and it may just be a great solution for keeping your rifle mags from riding up into your armor.
The Costa Leg Rig is manufactured by HSGI. It has integrated (non-detachable) HSGI TACO pouches that allow it to carry two of just about any type of rifle magazine and 3 of just about any type of pistol magazine (or flashlights, multi-tools, etc).
You can check out the Costa Leg Rig on CostaLudusGear.com.