OSX Sequoia 15.1.1 for Mac Pro 2009-12 +4,1 + 5,1 [New NVME M.2]

This will work with the Mac Pro 4,1 and 5,1 - years 2009/2012. [I can help you achieve this if you would like] Go to the Apple logo top left, About this Mac/System Report/Hardware Overview/System Firmware/Boot Rom Version to check what firmware you have.

eBay