The DIMMs, which are DDR-2 PC2-6400 units come in 1GB and 2GB kits. Kingston said they increase overall system performance when paired with some Nforce 500 motherboards, but didn't quanitify that.
The DIMMs operate at two volts, have 4-4-4-12 latency timings, and cost £123 plus VAT for the 1GB units and £221 plus VAT for the 2GB DIMMs. µ