4GB 240pin PC2-6400 DDR2-800 800Mhz Registered ECC DIMM. The price is for a single stick, all systems require this memory in matching pairs, must buy and install 2pcs, FOR A KIT BUY Qty 2.. Compatible memory for ASUS/ASmobile KFSN4-DRE/SAS Motherboard (DDR2-800MHz)