My primary survival kit is in Rubber Maid containers and in Igloo cooler in the back of my truck. There are two Camelbak backpacks with those containers -- a Mule and a Rim Runner the RR being the larger of the two at 1,342 cu in and the Mule having just 763 cubes.

Depending on time of year and conditions one of those two packs will be my GHB if I choose to leave the truck. If it's summer and very hot I may take both for the water.

The Rim Runner has an MSR mini-Works water filter and compatible Nalgene bottle, MSR MicroRocket Stove and Ti pot for cooking, plus other gear. The smaller pack is empty.

If I start walking the heaviest item(s) will be the water bladders.
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Better is the Enemy of Good Enough.
Okay, what’s your point??