These are premium quality belts and tyres from PRB (USA) and bundled by Analogue Depot. Search belts to learn more. 

Be careful of anyone offering PRB belts that do not come in the genuine package as seen in the image here.

This belt kit comprising capstan belt, counter belt and replacement idler tyre and is compatible with belts for the Nakamichi Sankyo transport BX100, BX125, BX150 cassette decks.