Why were pano cloths valuable in the mainland slave trade?

Pano cloths were highly valued in the mainland slave trade because they served as a standard form of currency for regional commerce during the 16th century.12

These unique textiles were produced in Cabo Verde by enslaved people who grew cotton, dyed it with dark indigo, and wove the fabric on narrow looms. The finished cloths were typically constructed by stitching together six strips of this fabric. Because of their standardized quality and utility, they became a primary medium of exchange used by traders to acquire enslaved people and other goods along the African coast.12