Thank everybody for your's answer ! SuperCriollo gave az good ides: Chest Rig... About the interesting post of Drake, i know about these game, witch i cant play because i dont have any low-cap; i'm more Skirmish than MilSim but im going to Dark Strike Of Hanois in august. In the night. So i think it's gonna be 4 pouch 4 Monster Energy Drink. Lol.
But seriously i think the final answer (counting you all) would be: For skirmish game, it's not very important (A little bit for Kill Rag) but for long-period game: water, bag of bb and Radios.
Also, lowcap, midcap or hicap is not the big thing to consider, it's how you play. Im not the kind of guy to put my gun in auto and shot as i reload. I'll shot all my round, stop, reload and then start again. Goal: Being as fast of low-cap people. It's not because i have all your 9 mag in one single mag that im better or worse...