Sunvalleytek via Amazon offer the RAVPower Bolt 4-Port USB Charger in Black for $17.99. Coupon code "GFY6PYN7" cuts it to $12.99. Plus, Prime members receive free shipping. (Non-members can spend $35 or more to qualify for free shipping; otherwise, it adds $6.98.) That's the lowest total price we could find by $4, although we saw it for $2 less last month. It features two 2.1-amp outputs and two 1-amp outputs.