Built for data-intensive operations that require an additional PCIe card, such as video and photo editing, and audio production, the Little Brother Thunderbolt 3 PCIe Expansion Chassis from Xcellon is an external enclosure that allows users to utilize PCIe cards with desktop systems whose PCIe slots are already occupied, as well as systems that do not have any PCIe slots, such as laptops and the 2017 iMac Pro. This enclosure is equipped with two Thunderbolt 3 ports, which provide bidirectional transfer speeds of up to 40 Gb/s and 15W of power delivery, a dedicated DisplayPort 1.2 port, and one PCIe 3.0 x16/x4 slot, which provides 25W of power and supports half-length, full-height, and double-width PCIe cards.

While one of the Thunderbolt 3 ports is used to interface with your Windows or Mac system, the second can be used to daisy-chain up to five additional devices to the enclosure, including additional storage, displays, and more. When connecting additional displays, the Thunderbolt 3 port can support one 5K display or one 4K display at 60 Hz, while the DisplayPort supports one 4K display at 60 Hz. Dual 4K displays are also supported at 60 Hz by using the DisplayPort and Thunderbolt 3 port, or by using one Thunderbolt 3 port with a dual display adapter.

Xcellon's Little Brother Thunderbolt 3 PCIe Expansion Chassis is plug-and-play compatible with Windows 7 and later and macOS 10.12 and later. Included is a 1.6' Thunderbolt 3 cable, a power adapter, and four rubber feet for horizontal orientation usage. Protection is provided by a limited 1-year warranty.