Upgrade Impact Charm through three ranks and it tops out at Flinch Free Lv3. The first rank costs 500z to craft, every rank after that is an upgrade. Some of the materials only come from Guardian Rathalos, Jin Dahaad and Quematrice.
Rank by rank
Impact Charm IRarity 3
Flinch Free Lv1: Prevents knockbacks.
Craftable · 500zImpact Charm IIRarity 4
Flinch Free Lv2: Prevents knockbacks. Tripping is reduced to a knockback instead.
Upgrade from previous rank · 1,500zImpact Charm IIIRarity 5
Flinch Free Lv3: Prevents knockbacks and tripping.
Upgrade from previous rank · 3,000z