For most applications our 3 mil pouches would be sufficient. You might consider a thicker mil if you are packaging a bony product where the bone might puncture the pouch. You can also use our Bone Guard product to prevent this from happening.
We usually recommend a thicker mil (4 mil, 5 mil, Re-Therm) when cooking at high temperatures (over 180°F) for long periods of time. For information on cooking in standard chamber pouches click here.