The advert suggests springs that are accurate, which is very necessary as crap springs can have actual rates as much as 10 % off the claimed rate.
The site has a decent looking spring selector.
I played with it a bit.
I used imaginary rider data.
A 235 # dressed rider on a 460 # wet 919.
Called it Standard/Sport Touring.
Did two useage scenarios, one for Normal Street the other Aggressive Street.
It called out 0.90 kg/mm for Normal and 0.95 for Aggressive.
I also played with the spring selector in an effort to find out if it will display what I'll call split rates, such as 0.925, where you are forced to use a 0.90 and a 0.95 to get the 0.925 and typically have to buy two sets of springs and only use one from each box. I could not spook the selector into any split rate selections. It turns out our Imaginary Rider is known to us, and we've had some back and forth on spring rates. I think he is going to end up trying 0.925s.