Yes, this is correct for the Lexmark CX517de printer, it's listed as correct on the Lexmark website.
Hi again, you can find the Lexmark CX310dn imaging units on the following pages...
Colour and black: https://www.tonergiant.co.uk/product/Lexmark-700Z5-Black-and-Colour-Imaging-Kit-70C0Z50-19900/
Black only: https://www.tonergiant.co.uk/product/Lexmark-700Z1-Black-Imaging-Unit-70C0Z10-19899/
If you need any more help, let me know!