Reading the above there does seem to be some confusion about the use/size of a possibles pouch/bag.
If I may make so bold (bold not bald) I will endeavour to define the differences as I see them.
Possibles pouch - a small pouch worn on a belt (with your knife) that contains those most essential items, ie fire lighting kit and paracord. Its purpose is to act like the woodsman survival kit and is worn all the time, the last things you should take off are your pants and then your possibles pouch! It should be unobtrusive (so your not inclined not to wear it) and can be worn with trousers, shorts etc.
Possibles bag - larger item, can be a shoulder bag (respirator haversack) or a small day sack (plce single jet pack) this contains slightly more kit predominately water and Metal mug or pot as well as other useful items like folding saw. poncho ect - this by its nature is taken off and on and in worse case scenerio could be lost which is why you have your possibles pouch on your belt!
After this we are then onto packs and full kit, bashas, sleepng bags ect ect.