Listed under Yoruichi's Equipment section on her Wikipedia page, they're are described as " A set of metal gloves and boots, invented by Kisuke Urahara, designed specifically to counter an Arrancar's Hierro during hand-to-hand combat. They are exceptionally durable, protecting the wearer's limbs even during the moment of their destruction".
These tools, dropped only by NPC Numero and Espada Arrancar on a moderately low frequency, do not actually give you a boost. Rather, despite their listed intention only working on arrancar, actually negate 10% of your target's defence despite their race. In similar fashion to Bakkoto the AHA is not used in conjunction with racial abilities that require the wielding of a weapon such as Fullbrings, Zanpakuto, Bows, Resureccion, etc. This is the trade-off for adding a defense pierce to your standard attacks.
These tools, dropped only by NPC Numero and Espada Arrancar on a moderately low frequency, do not actually give you a boost. Rather, despite their listed intention only working on arrancar, actually negate 10% of your target's defence despite their race. In similar fashion to Bakkoto the AHA is not used in conjunction with racial abilities that require the wielding of a weapon such as Fullbrings, Zanpakuto, Bows, Resureccion, etc. This is the trade-off for adding a defense pierce to your standard attacks.
