The original fork springs are only designed for ordinary road use. Under racing conditions, use is restricted to short rest intervals.
Ohlins fork springs are approximately 10% harder than standard
springs, which means they greatly increase the possible operating range
of the original fork.
Ohlins fork springs are developed specifically for Ohlins cartridge kits and front forks. But they are also in itself a great front end upgrade and as such available as a spring upgrade for most major bike models.