Part JD521A is compatible in the following Models:

HPE FlexNetwork MSR93x Router Series

HPE MSR931 Router - JG514B
HPE MSR931 Dual 3G Router - JG531B

HPE MSR Router Flexible Interface Cards (FIC)

HPE 8-Port Enhanced Serial FIC A-MSR Mod - JD580A
HPE 4-Port Enhanced Serial FIC A-MSR Mod - JD584A

HPE Router DCE Cables

HPE X200 V.24 DCE 3m Serial Port Cable - JD521A

HPE Router High-performance Multifunction Interface Module (HMIM)

HPE MSR 4p Enh Sync/Async Srl HMIM Module - JG442A
HPE MSR 8p Enh Sync/Async Srl HMIM Module - JG443A

HPE Router Multifunction Interface Modules (MIM)

HPE 2-Port Enhanced Serial MIM A-MSR Mod - JD540A
HPE 4-Port Enhanced Serial MIM A-MSR Mod - JD541A
HPE 8p Enh Sync/Async Interface A-MSR Mod - JD552A