Geek Buying offers the Xiaomi Piston 3 In-Ear Headphones in Black for $15.99 with free shipping. That's $4 below last month's mention (which was bundled with a smart key) and the lowest total price we could find by $3. It features a frequency response of 20Hz to 20,000KHz and a gold plated 3.5mm plug. Deal ends May 6.