Good for upgrading a current system or even for a new system as it works out at £52 for 4GB which is cheap by current prices.
They also have Geil RAM of the same spec at the same price but that states usually dispatched in 10 days; see 1st post for a link to that.
Memory Size: 1GB
Memory Type: PC6400 DDR2
Memory Speed: 800MHz
Form Factor: 240pin for Desktop Computers
DDR2 PC2-4200 (533 MHz Bus Speed)
DDR2 PC2-5300 (667 MHz Bus Speed)
DDR2 PC2-6400 (800 MHz Bus Speed)