Included are multiple mount claws, and multiple contact pins following the circumferential direction of a second mount. The second mount can rotate to a first state where multiple claws of a first mount are inserted between the multiple mount claws, and a second state where the multiple mount claws engage the claws in a center axis direction. In the first state, a first mount claw is included in an angle range where a first contact pin of the multiple contact pins and a center axis of the mount are connected in the radial direction of the mount, and a first contact face of the multiple contact faces and the center axis are connected in the radial direction of the mount. The first contact pin and the first contact face come into contact first when rotating from the first state to the second state.