Also known as: カードデッキ, ベントホルダー
Tools from “Kamen Rider Ryuki”. They are cases for storing Advent Cards.
By holding it out towards the reflective surface, the transformer is equipped with V Buckle. Attaching it to V Buckle as it is transforms the transformer into a Kamen Rider.
When the owner enters into a contract with a Mirror Monster, a crest symbolising that Monster appears on this surface.
In “Kamen Rider Dragon Knight”, it was also used as a substitute for a Shield.