Walkman battery case. Since I don't have the main unit, I don't know which model it fits. There is no rust inside, and it's clean with almost no signs of use. Since the model number is unknown, I'm providing the size of the charging terminal. From the center terminal to the terminals: right approx. 1.9cm, left approx. 1.45cm. [Product Name] Walkman Battery Case [Color] Black Clear Please refrain from purchasing if you are nervous about home storage. Thank you. Thank you for viewing.