Introduced at NAMM 2012, the ULX-D became a quick favorite of ours based on the great flexibility and outstanding sound. Shure has now re-packaged the receivers in both dual and quad configurations allowing for significantly denser channel counts in a given rack space. They've also included some additional cool features like Danté and RF cascade. They also came up with a new high-density mode which packs even more channels in a given RF band. It's impressive stuff.