Bestekmall offers the Bestek 4-Port USB Charger in Black or Orange for $18.73. Coupon code "FORPRO60" cuts the price to $7.49. (You must be signed in to use the coupon.) With free shipping, that's $2 under last month's mention and the lowest price we could find by $9. It supports international 100-volt to 240-volt input.
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