Echo Express SE IIIe is a 3-slot Thunderbolt 3 desktop expansion system for PCIe cards. Connect three full-height, half-length+ PCIe cards to computers with thunderbolt 3 ports.¦Although thin Mac, Windows, and Linux computers with Thunderbolt 3 ports offer processing power to spare, for many users (such as pros in the creative fields) onboard processing power alone is not enough. Sonnet's Echo Express SE IIIe is a compact, desktop Thunderbolt 3 to PCIe card expansion system that enables you to connect three professional PCIe cards at the same time to any computer with Thunderbolt 3 ports.