Massdrop offers the Exotac FREEKey System 3-Pack for $14.99 plus $2.91 for shipping. That's a buck under our January mention and the lowest total price we've seen. (It's a current price low by $3.) Each set is made of stainless steel and features one master ring and three smart rings. Deal ends July 5.
Note: It's scheduled to ship on July 17.