As one of its daily deals, Amazon offers Prime members the Logitech M557 Bluetooth Mouse in Dark Grey, model no. 910-003971, for $20.75 with free shipping. (Non-members can spend $49 or more to qualify for free shipping; otherwise, shipping costs $8.15.) That's a buck under our mention from two weeks ago and the lowest total price we've seen. (It's the best deal now by $5.) This wireless mouse features customizable buttons, a vertical and horizontal scroll wheel, optical sensor, and ambidextrous design. Two AA batteries are required, included. Deal ends today.