I've recently upgraded the RAM in my Synology NAS, so the original 4GB UDIMM is not much use to me any more.

DDR4 2666 4GB CL19 ECC

The product compatibility list shows this as being compatible with RS2821RP+, RS2421RP+, RS2421+ Synology NAS models.

The part number is D4EU01-4G, and it looks to be available new for ~$170.

I'm looking for $100 for it, pick up in Christchurch or shipping additional.