HP lists this spare part number for the HP Elite x2 G8 Tablet in its Maintenance and Service Guide (printed p.25).
Source notes
HP Maintenance and Service Guide for the HP Elite x2 G8 Tablet (Document Part Number M65100-001), spare parts table, printed p.25: "system memory, OSR with thermal material M51657-001". Read from the cached HP manual (via FDY-MM-015-R1).