QSA Adapter - 40G QSFP+ to 10G SFP+ Converter Module for Mellanox MAM1Q00A-QSA-SP, Dell 407-BBRO, Juniper, Arista, Extreme and More.

This doesn’t work in my Cisco C9500-24Q switches. Instead of passing through the transceiver’s details so the switch can identify it and link at 10Gb, it emulates a “QSFP 40G CU1M” at 40Gb and refuses to link up even though there’s appropriate power on the Rx and Tx. I’m really not sure what is going on with the 3rd party market these days, but this is the 3rd brand of this module I’ve tried in a week and none work properly as my official Cisco modules do, or as 3rd party modules from a year or two back do.