Fantastic Direct Deals via Amazon offers Amazon Prime members the refurbished Belkin Linksys 802.11ac Wireless Mini AC580 Dual Band USB Adapter, model no. AE6000, for $18.99 with free shipping. (Non-members can spend $35 to qualify for free shipping; otherwise, it adds $8.20.) Aside from the below mention, that's $2 under our mention from a month ago and the lowest total price we've seen for a refurbished model. It's also $16 below the best price we could find for a new one. Features include a maximum speed of 430Mbps, dual-band functionality, and WEP/WPA/WPA2 encryption. No warranty information is provided.
A close price: Voodublu via eBay offers it with a 90-day Linksys warranty for $19.99 with free shipping.