Well they quote 5-600, however I reckon around 550ish is about right, also judging by others results, they get around that figure. I was looking initially for between 5-600, however changed my mind when the car arrived from Japan.
These are popular kits in Australia/Japan and US. As they were only special order from HKS I don't think anyone ran them in the UK or even stocked them...
If you know Skylines these are used on them from time to time and compared to the HKS 2530's, which is an awesome setup for the GTR on the street.
They will work as the current setup does and are a direct replacement.