The listing, Server/Desktop RAM has ended.
2x 512MB DDR PC-2100 Registered/Buffered ECC RAM.
These are two DIMMS for your older server or once higher-end desktop. These are registered/buffered ram, so check your motherboard/computer information carefully. (The HP part number is included in the third picture, if you have the misfortune of needing to search through HP documentation.)
AFAIK, you can use ECC ram in a non-ECC system, but you can not use registered/buffered ram in an unregistered/unbuffered system.
Free Shipping in the US. (I ship with Delivery Confirmation.)
Free Shipping to Canada. (Due to cost, I will not provide tracking number/Delivery Confirmation. I will only provide a receipt as proof of shipping.)
Everywhere else, shipping at cost (check USPS website) via PayPal.