ConnectX-4 LX, PCIe version with low profile bracket. These have a Lenovo Part Number (01GR253) & appear to be the same as MCX4121A-ACAT. $20 w/ free shipping.
I bought two of these from this seller recently when they were at a higher price ($24.99). Mine came packed well and had the newest firmware.
Lenovo Mellanox CX4121A ConnectX-4 Lx 2-Port PCIe Ethernet Adapter Card, 01GR253 | eBay
Lenovo Product Guide info: https://lenovopress.lenovo.com/lp0098-mellanox-connectx-4
I bought two of these from this seller recently when they were at a higher price ($24.99). Mine came packed well and had the newest firmware.
Lenovo Mellanox CX4121A ConnectX-4 Lx 2-Port PCIe Ethernet Adapter Card, 01GR253 | eBay
Lenovo Product Guide info: https://lenovopress.lenovo.com/lp0098-mellanox-connectx-4