As one of its daily deals, Amazon offers its Prime members the Logitech Wireless Performance Mouse MX, model no. 910-001105, for $39.99 with free shipping. (Non-members can spend $49 or more to qualify for free shipping; otherwise, it costs an extra $8.88.) That's $5 under our July mention and the lowest total price we've seen for a new unit. (It's a best now by $19.) It features four thumb buttons, a scroll wheel, and Logitech unifying USB receiver. Deal ends today.