Agile Maiden

Combat

The Gray Maidens’ signature armor hinders you less than others.

Prerequisite: Str 13; Dex 13; Endurance or armor training class feature; proficiency with heavy armor.

Benefit: For the purpose of class features (such as a ranger’s combat style, a barbarian’s fast movement, or a magus’s spellcasting), you treat Gray Maiden plate as medium armor or heavy armor, whichever is more beneficial to a given ability. This does not affect the armor’s statistics, and it is still considered heavy armor for all other purposes.

Source: Adventurer's Guide