What is the Sandstone QDD-400G-LR4-10-ST?
The Sandstone QDD-400G-LR4-10-ST is a QSFP optical transceiver module, listed by the manufacturer as "Compatible QSFP-DD 400G-LR4-10, SMF 10 km; Standard Temperature (0 through 70C); Duplex LC/PC Receptacle". It is part of Circular Telecom's surplus and refurbished telecom/IT equipment inventory.