Streetwise aux belt

Anyone here tell me the correct belt for a Streetwise diesel? My son ordered a belt for his Streetwise (without AC) and it's far too small. The belt was listed as for a none AC diesel of the correct year. My understanding is that the correct belt is one for a car 'with' AC because of the idler that replaces the AC compressor. Is this correct and, if so, why do they sell them for none AC cars?

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