Rucksacks
Rucksacks raise item capacity by tier: Simple has 32 slots, Rugged 48, Heavy Duty 64 and Extended 96. The listed hide requirements are two boar hides, two tapir hides, four dingo pelts and one Undying Bear Leather.
How it works
The highest tier is marked as requiring Path of the Hunter. The guide notes that collecting all hides for every maximum upgrade may be impossible without larger rucksack bags, making capacity itself relevant to gathering materials.
The tradeoff
Larger capacity can help with collecting the hides needed for other upgrades.
Read the supporting references
Single-player crafting upgrades and skill-tree progression in Far Cry 3: crafted-equipment categories and three broad skill-tree orientations. The evidence supports capacity details for listed crafted items and general focus descriptions for the trees. Guidance explains the referenced mechanics; it is not a tested damage ranking. Check the stated edition and source version before applying a patch-specific detail.