What is the X2129A?
The X2129A is a SFP+ optical transceiver, listed by the manufacturer as "10GbpsDualRateSFP+SR (ShortReach) TransceiverUse with MMF (Multi-Mode Fiber 850nm) cable with LC connector , support 1G and 10G dual rate". It is part of Circular Telecom's surplus and refurbished telecom/IT equipment inventory.